RESIDENT EVIL
ZERO
TEXT LOGO PLACEHOLDER — SEND COVER ART TO REPLACE

RESIDENT EVIL 0 (ZERO)

100% Completion Guide — GameCube (2002) & HD Remaster (2016)
2
Characters
5
Areas
7
Bosses
29
Files
11
Weapons
100
Leech Charms

Game Overview

Released for the Nintendo GameCube in 2002 and remastered in HD in 2016, Resident Evil 0 is a prequel to the original Resident Evil. It follows S.T.A.R.S. Bravo Team medic Rebecca Chambers and death-row ex-Marine Billy Coen on the night of July 23, 1998, as they fight through a stranded Umbrella train and the hidden facilities beneath the Arklay Mountains.

DetailInfo
TitleResident Evil 0 / Biohazard 0
ReleaseGameCube 2002 · HD Remaster (PS3/PS4/Xbox/PC) 2016 · Switch 2019
Developer / PublisherCapcom
GenreSurvival Horror (fixed camera)
Playable CharactersRebecca Chambers & Billy Coen (partner-swap system)
Main AntagonistJames Marcus / the Queen Leech
Areas (in order)Ecliptic Express → Training Facility → Laboratory (Church) → Factory → Treatment Plant
SettingJuly 23, 1998 — Arklay Mountains (the night before Resident Evil 1)
100% Playthrough~8–10 hours (plus Leech Hunter for infinite weapons)

Core Mechanics — Read This First

Two systems make Resident Evil 0 different from every other classic RE game. Understanding them is the whole guide.

Partner Zapping (two characters)
You control one character at a time and instantly “zap” control to the other; the one you are not controlling becomes an AI Partner. You can order the partner to follow you or stay put, and set it to attack on its own or hold fire (hold fire to save shared ammo). You can switch even when the two are in different rooms — almost every puzzle is one character working a mechanism while the other stands somewhere else.
No Item Boxes — you DROP items
There are no storage chests anywhere in this game. To manage space you drop items on the floor; they stay exactly where you leave them and can be collected later (the map marks rooms that hold dropped items). Each character has 6 inventory slots; the Hunting Gun, Shotgun, Grenade Launcher and Hookshot each take 2 slots. The two hand items to each other in person when standing together.
Rebecca vs. Billy
Rebecca Chambers is physically weaker (dies faster) but is the only one who can mix herbs and chemicals (she carries the Mixing Set) and squeeze through narrow gaps/vents. Billy Coen takes less damage, hits harder, and is the only one who can push/move heavy objects and boost Rebecca to high places.
Because there is no item box, and areas become sealed off behind you, sweep every room before moving on and stage heavy items where the guide tells you. Files and items left in a finished area are gone for good.

Story Synopsis

S.T.A.R.S. Bravo Team is sent into the Arklay Mountains to investigate cannibal murders, but their helicopter crashes. Rookie medic Rebecca Chambers boards a stopped Umbrella train, the Ecliptic Express, and finds its passengers turned into leech-covered zombies. Aboard she meets Billy Coen, a former Marine being transported for execution. Forced to work together, the two survive the train — which is hijacked and crashes into a hidden Umbrella training facility.

Beneath it they uncover the work of Umbrella co-founder Dr. James Marcus, who bred the leech creatures and was assassinated in 1988 on Spencer’s orders by his protégés Wesker and Birkin. A hooded figure conducting an orchestra of leeches turns out to be the Queen Leech — a mutant leech that consumed Marcus’s corpse, took his memories and face, and unleashed the t-Virus for revenge. After the final battle in the collapsing treatment plant, Rebecca and Billy destroy it. Rebecca reports Billy as dead to let the framed man go free, then heads for the Spencer Mansion — leading directly into the first Resident Evil.

Characters

Rebecca Chambers
18-year-old S.T.A.R.S. Bravo Team medic and chemistry graduate. Weaker in a fight, but mixes herbs/chemicals and fits through small gaps. Survives into Resident Evil 1.
Billy Coen
Former U.S. Marine lieutenant, court-martialed and sentenced to death after being scapegoated for a wartime massacre. Stronger and tougher; cannot mix herbs. Innocent — Rebecca lets him walk free.
James Marcus / Queen Leech
Umbrella co-founder and t-Virus pioneer, murdered in 1988. The Queen Leech absorbed his body and identity and masterminds the outbreak as his “revenge.” The final boss.

Difficulties — Easy, Normal & Hard

Resident Evil 0 has three difficulties: Easy, Normal and Hard, on both the GameCube original and the HD Remaster. All three are selectable from the start, and the difficulty is locked to that save file once you begin.

Every code and solution in this guide works on all three difficulties. Difficulty never changes a puzzle answer — the clock (8:15), the power regulator, the torch order, 385, 4863, the power grid and the chess board are identical on Easy, Normal and Hard. The only two puzzles that vary are the train brakes and the conference-room terminal code, and those are re-rolled every playthrough regardless of which difficulty you picked.

All 29 files exist in the same places on every difficulty too, so a 100% file run is identical whichever setting you choose.

What Actually Changes

Difficulty in this game is almost entirely about supplies, not about the map. Enemies hit harder and soak more damage as you go up, and the game hands you far less to work with — both smaller pickups and fewer pickup spots.

Supply (full playthrough)EasyNormalHard
Handgun rounds~950~635~545
Shotgun shells~133~112~91
Green Herbs~42~26~22
First-Aid Sprays~16~9~8
Ink Ribbons~70~46~34
Myth-buster: the number of enemies does not change between difficulties. The same zombies, dogs, Hunters and Eliminators stand in the same rooms on Easy and on Hard — they simply take more punishment and deal more damage. Easy is not a shorter game, it is a better-stocked one.

Saving costs an Ink Ribbon on every difficulty (this game removed item boxes, not ribbons). Only the supply changes — and the ribbon itself is colour-coded blue on Easy, white on Normal and red on Hard.

Which Difficulty Should You Play?

DifficultyRanksSupplies & EnemiesBest For
EasyNo rank at allRoughly double the ammo and healing of Normal, softer enemies.Learning the routes and collecting all 29 files with no pressure. No results screen means no Sub-Machine Gun and no Rocket Launcher — practice, not progress.
NormalFull ranksThe intended balance.The default choice for a first serious run or a rank attempt. If you only play the game once, play it here.
HardFull ranksAbout 15% less handgun ammo than Normal, fewer herbs and sprays; enemies hit harder and take more.A resource-management game — same map, same puzzles, same enemy placements. It is about not wasting a single bullet, not about reflexes.
The Easy trap — read this before you touch Leech Hunter. Leech Hunter runs at the difficulty of the cleared save you launch it from, and its infinite-ammo rewards are locked to that same save and difficulty. Clear Leech Hunter from an Easy file and your infinite ammo only works on Easy — where no rank is ever awarded, so it can never help you unlock anything. Always do Leech Hunter from a Normal or Hard clear.

Beating Hard Mode

Everything below is good practice on Normal — on Hard it stops being optional.

1
Run past almost everything. Learn the step-back dodge and walk around zombies, crows, spiders and Eliminators rather than fighting them. Ammo spent on trash is ammo missing at the finale.
2
Never shoot a Leech Zombie or Mimicry Marcus. Bullets are wasted on them — only fire kills them. Use Molotov Cocktails (make them from empty bottles and keep making them; they are the free anti-leech resource) and save your Flame grenade rounds. Better still, sprint past them.
3
Reserve the Magnum completely for the endgame. Aim to reach the Treatment Plant with roughly 20 Magnum rounds untouched, and keep at least 2 Grenade Launcher rounds spare for the final Queen Leech phase.
4
Match the round type to the enemy. Acid rounds for Hunters and the Centurion, Flame/Incendiary for anything leech-based. The Grenade Launcher is the efficiency weapon of the game — a Hunter costs about one grenade plus a pistol shot, versus dozens of handgun rounds.
5
Keep Billy in front. Rebecca takes noticeably more damage, and that gap widens on Hard. Control Billy for fights and use Rebecca as the pack mule — with two exceptions: Rebecca throws Molotovs faster, and she is the only one who can mix herbs.
6
Use the knife and fire point-blank. Point-blank shots do meaningfully more damage than shots at range in this game, and the knife is genuinely viable — the Stinger stuns after every hit, so the train boss can be killed without spending a single shell.
7
Skip the Hunting Gun, take the Shotgun. The Shotgun you find in the facility is strictly better and saves you juggling two-slot weapons. Build the Custom Handgun (Duralumin Case, code 385) as soon as you can — the improved fire rate carries the whole midgame.
8
Rotate your save slots. Ribbons are tighter on Hard but still adequate; the real danger is overwriting your only save after wasting ammo. Keep two or three slots rolling so a bad stretch is recoverable — running dry at the last boss with no earlier save is the classic Hard-mode dead end.

The Two Hard-Mode Spikes

Bosses do not get new attacks on Hard — the game scales health and damage globally, so every fight simply lasts longer and punishes harder. Two of them are where Hard runs actually die:

Proto-Tyrant, first encounter (Factory)
The hardest fight in the game on Hard, because Rebecca faces it alone in a cramped arena with the game's most fragile character. Keep moving, fire the Magnum only when you have a clean angle, and reposition immediately — do not stand still lining up shots. A Shotgun blast to its back knocks it down and buys you free follow-ups. This is the fight players over-spend on and then arrive at the finale empty.
Queen Leech, final phase (Treatment Plant)
An attrition gauntlet where earlier waste comes due. Remember you are not trying to kill it — it is immune to gunfire. Billy only has to hold its attention while Rebecca works the shutters, so shoot to pull aggro, not to win. The on-screen timer is more generous than it looks. Fire at point-blank for maximum damage and aim for the tail to disorient it.
The other five bosses are comfortable if you bring the right tool: knife or Shotgun for the Stinger, the exposed white underbelly for the Centurion, and roughly five Grenade Launcher rounds to stun-lock the Infected Bat to death — the cheapest answer to that fight.

Ranks, Unlocks & the Best Order to Play

Your rank depends on clear time only. Saves, retries, healing items and even unlocked infinite-ammo weapons do not lower it — and the thresholds are the same on Normal and Hard.

RankClear timeReward
S3:30:00 or fasterInfinite Rocket Launcher (plus the Sub-Machine Gun)
A3:30:01 – 5:00:00Infinite Sub-Machine Gun
B5:00:01 – 7:00:00
C7:00:01 – 9:00:00
Dslower than 9:00:00
Easyany timeNo rank and no results screen
The efficient route through everything
1. Clear the game on Normal at your own pace (this unlocks Leech Hunter, Wesker Mode and the costumes). 2. Play Leech Hunter from that Normal save and collect all 100 charms for infinite ammo. 3. Use that infinite ammo on a Normal speed run under 3:30 for the S rank and the Rocket Launcher. 4. Take Hard on last, with the unlocked weapons available if you want them.
Speed-run essentials: fight as little as possible, skip the Hunting Gun, build the Custom Handgun early, and plan your item-drop points in advance — with no item boxes, sloppy item routing is what separates a five-hour run from a three-hour one. Pausing does not advance the timer, so you can stop and check the route.

Leech Hunter & Wesker Mode Difficulty Rules

Leech Hunter inherits its difficulty
You cannot pick a difficulty for Leech Hunter — it runs at the difficulty of the cleared save you launch it from, and its rewards stay tied to that save and difficulty. Its own rank is based on how many of the 100 charms you collect (50 blue for Billy, 50 green for Rebecca), and both characters must survive and reach the exit.
RankCharmsReward
A100Unlimited ammo for all weapons
B90–99Magnum Revolver (then found on the train)
C60–89Unlimited Hunting Gun ammo
D30–59Unlimited handgun ammo
E0–29Sub-Machine Gun ammo
Leech Hunter’s item layout is randomised across a few sets, and you can identify yours from the herbs in the main hall at the start — so if you want a particular weapon set, reset at the beginning rather than discovering it forty minutes in. Clear each room of enemies before collecting its charms, and leave the nearby rooms for last, because some rooms respawn zombies once you are near the end of the count.
Wesker Mode is locked to Normal
Wesker Mode (HD Remaster and Switch only) has no difficulty option — it always runs on Normal, and it awards no rank, so it cannot be used for an S-rank run. It is easier in practice anyway: Wesker’s Death Stare costs no ammunition at all, which removes the game’s entire resource problem, and his Shadow Dash lets you skip most fights. He can also mix herbs, which Billy cannot. Any Leech Hunter infinite ammo you have earned still applies here.

Story Walkthrough — 5 Areas

A complete step-by-step for a 100% run: every key item, every file, every important pickup and every puzzle solution is written in order below. The area order is Ecliptic Express → Training Facility (+ basement) → Church/Laboratory → Factory → Treatment Plant. Pick a chapter below, then use the Previous / Next buttons at the bottom of each chapter to move through the game.

AREA 1Ecliptic Expressthe Umbrella train (Rebecca, then co-op)
1
Playing as Rebecca, you start in the rear car with your Handgun. FILE #1 Player’s Manual 1 is already in your inventory as the tutorial file. Near the wrecked prisoner-transport at the very start, grab FILE #2 Court Order for Transportation (it describes the convict, Billy).
2
Move forward through the passenger cars, killing or slipping past the zombies (kill only the nearer one to save ammo). Note the stairs up to 2F — you return here later with the Hookshot.
3
In the sleeper car, take the KEY ITEM Dining Car Key from the train-employee’s corpse by the engine door. Grabbing it triggers a scene: you glimpse Billy, a dying Bravo teammate collapses, and Cerberus (zombie dogs) attack — fight them off and loot the bodies for Handgun Ammo.
4
Sweep the compartments: Room 202 has FILE #3 Passenger’s Diary and Handgun Ammo. Room 201 (save room) has FILE #4 Investigation Orders, an Ink Ribbon, a Green Herb and a typewriter — save here.
5
Use the Dining Car Key on the Dining Car (1F): FILE #5 Notice to Supervisors is on a table by the stairs. (Optional: empty bottles + a gas tank here can be combined into Molotov Cocktails.)
6
On Dining Car 2F the first Leech Man appears — don’t fight it, retreat toward the stairs. This triggers the team-up: Billy saves Rebecca. Partner-zapping now unlocks, and FILE #6 Player’s Manual 2 is added automatically.
7
As Rebecca, climb the ladder from Dining Car 2F onto the train roof and reconnect the severed power cable; a scene drops her into the Kitchen 2F.
8
In the Kitchen 2F, take the KEY ITEM Conductor’s Key, place it in the dumbwaiter (service lift) and send it DOWN.
9
Zap to Billy in the Kitchen 1F, take the Conductor’s Key from the lift, and open the Conductor’s Room: grab the MAP Train Map, FILE #7 Note from Conductor, and note the KEY ITEM Briefcase (two ring-shaped slots — solved later). Press the switch to drop the ladder to the bar car.
10
In the bar car take the Ice Pick from the trolley. In Room 101 grab the WEAPON Hunting Gun (+ shells) and a First-Aid Spray; equip the Hunting Gun.
11
BOSS Stinger (giant scorpion) ambushes in the bar — fight as Billy: back to the doorway, aim down at its head, fire the Hunting Gun and reload every 2 shots. It drops the KEY ITEM Panel Opener. (Full strategy in the Bosses tab.)
12
Send the Ice Pick UP the dumbwaiter to Rebecca; she uses it on the jammed/iced kitchen door to free her route.
13
As Billy, use the Panel Opener on the silver kitchen wall panel to open the vent. Rebecca crawls through and takes the KEY ITEM Gold Ring.
14
On the outside balcony, collect the KEY ITEM Hookshot (+ FILE #8 Hookshot Operator’s Manual, automatic). Fire the Hookshot to reach the roof, drop through the hole into a cabin, and open the Jewelry Box for the KEY ITEM Silver Ring — then hurry back before the leeches swarm.
15
Give both rings to whoever holds the Briefcase; insert the Gold + Silver Ring → the case opens for the KEY ITEM Blue Keycard.
16
Use the Blue Keycard on the driver’s-cabin door. Inside: the KEY ITEM Magnetic Card and FILE #9 Brake Operation Manual (automatic).
17
PUZZLE Train brakes (two panels — rear balcony + driver’s cabin, one character at each, activated with the Magnetic Card). Each screen shows a randomized target; press ten digits (1–9) that add up to it. Fast method: press as many 9s as fit, then fill the remainder (e.g. target 67 = seven 9s = 63, then 2+1+1). The cabin panel’s screen is broken, so track that one yourself.
MISSABLE Once both brakes engage, the train crashes into the training facility and you can never return. Sweep every car for herbs, ammo, ink ribbons, the First-Aid Spray and all train FILE files before the final brake.
Chapter 1 of 6
AREA 2Umbrella Training Facilitythe management-training mansion
1
Climb from the crash up through the flooded sewer into the Main Hall (typewriter + Ink Ribbons — your save point for this area). Note the statue with the scales here — that’s the basement lock you open at the end.
2
Up to 2F: in the small raven room grab the KEY ITEM Crank Handle and FILE #10 Notice to All Staff (its hint is 8:15). Ignore the ravens.
3
Sweep 2F: FILE #11 Regulations for Trainees (conference room, + a typewriter), and in the storage room the MAP Training Facility Map and Microfilm A.
4
Attach the Crank Handle to the lift: stand Rebecca on it, order her to stay, zap to Billy and crank her up to 3F (the pair splits). Rebecca clears the mutated insects up top.
5
As Billy, take the WEAPON Grenade Launcher (+ grenade rounds) from the art-storage room and note the White Statue there; find the WEAPON Shotgun and the Black Statue in the storeroom.
6
Behind the red door: FILE #12 Assistant Director’s Diary. Push the table to the fireplace, climb up and take the KEY ITEM Iron Needle from the trophy. In the kitchen grab the Lighter Fluid and combine it with Billy’s Lighter.
7
PUZZLE Clock: take the Iron Needle to the 3F clock, mount it, then set the minute hand to III (15) and the hour hand to VIII (8) = 8:15. Two clock-marked doors open.
8
Get Microfilm B (above the eastern fireplace) and FILE #13 A Verse of Poetry there. Put both microfilms in the projectorFILE #14 Microfilm Image (automatic — it shows the desk grid) → take the MO Disk.
9
PUZZLE Conference desks (randomized): insert the MO Disk in the terminal to read a two-character code, match each character to the desk grid, set both characters to solo, stand one at each coded desk and press together. The armored doors open.
10
In the Medicine Room grab the Green Chemical (NE corner) and FILE #15 First Investigation Unit Notes (on a bed).
11
PUZZLE Chess (Marcus’s office): make the big board match the small reference board — move only the piece that’s out of place (a wrong move releases poison gas). Reward: the KEY ITEM Book of Evil and FILE #16 Marcus’ Diary 1. Examine the Book of Evil for the Black Wing; combine Black Wing + Black Statue = Statue of Evil.
12
Use Billy’s lit Lighter on the lamp by the library, go in and push the bookshelf for the Book of Good; examine it for the Angel Wings; combine Angel Wings + White Statue = Statue of Good.
13
PUZZLE Statues: place the Statue of Good and Statue of Evil on the Main-Hall scales — the basement staircase opens under the painting. Save and stock both characters before descending.
Chapter 2 of 6
AREA 2BTraining Facility Basementbeneath the mansion
1
Descend the statue staircase to the B1 corridor (venom-spitting spiders — shoot them on the ceiling). In the Observation Room: FILE #17 Correctional Institute Inmates List, a Blue Herb, and a typewriter (save).
2
Billy boosts Rebecca up through a wall grate — she goes on alone to the Power Room: FILE #18 About the Power Regulator (target = 70).
3
PUZZLE Power Regulator: set the five switches UP, UP, DOWN, UP, UP = 70 to restore power. (This separates the pair; control returns to Billy.)
4
As Billy, fight through the Eliminators (mutated apes) toward the Large Hall.
5
BOSS Centurion (giant centipede): Billy fights alone while Rebecca is held — shoot the white underbelly when it rears up, backing off between hits (Shotgun / Grenade Launcher). Free Rebecca.
6
Cage crank: Billy raises the suspended cage and Rebecca takes the KEY ITEM Facility Key (Fire Key — fire emblem). It opens the fire-marked kitchen and offices.
7
PUZZLE Piano (2F bar): Billy plays the piano to open the hidden wine room; send Rebecca in for the KEY ITEM Battery (+ Magnum ammo, empty bottles). Billy plays again to reopen the door so she can leave.
8
Use the Fire Key on the kitchen for the Lighter Fluid (fuel the Lighter). PUZZLE Animal torches: with the lit Lighter, light the animal statues weakest→strongest: Deer → Wolf → Horse → Tiger → Snake → Eagle — the passage opens.
9
In the bunk room take the KEY ITEM Unity Tablet (west fireplace) and FILE #19 Management Trainee’s Diary.
10
Down in the B3 testing area (spiders): take the KEY ITEM Locker Key (waterfall room) and open the locker for the Duralumin Case. PUZZLE Duralumin Case: examine it for the code, enter 385Handgun Parts → combine with a Handgun = WEAPON Custom Handgun.
11
Control-panel / Hunter room: Rebecca works the left then center buttons while Billy collects Acid rounds and hits the red button — Hunters spawn; kill them with Acid grenades. Grab the second KEY ITEM Facility Key (Water Key — water emblem) from the hole they came out of; it opens the water-marked corridors.
12
Get the KEY ITEM Vice Handle (broadcast/AV room) and use it on the vise to release the KEY ITEM Obedience Tablet. Power the front-yard lift with the Battery, ride up, and have Billy push a crate to reach the KEY ITEM Discipline Tablet.
13
PUZZLE Observatory: on 3F take the door between the two suits of armor to the observatory and slot Unity + Obedience + Discipline — the tower lowers down to the Laboratory.
Chapter 3 of 6
AREA 3Church & LaboratoryMarcus’s underground lab
1
Head down the outdoor path to the church (grab Shotgun Ammo in the right-hand tower). At the church door, stand Rebecca on the floor tile to hold it open and send Billy in.
2
Take the right-hand save room inside: Incendiary (Napalm) grenade shells, ammo, Ink Ribbons, typewriter — load the Grenade Launcher and save.
3
BOSS Infected Bat (in the church): fight as Billy — aim up and fire the Grenade Launcher/Shotgun as it swoops; ignore the small bats. (See Bosses tab.)
4
After it dies, use the Hookshot on the church wall to reach the roof, drop to the back yard and pull the lever to restore elevator power; ride down into the Laboratory.
5
In the lab (save), send Billy up via the Hookshot. Grab FILE #20 Marcus’ Diary 2 (Reference Room) and FILE #21 Old Photograph (Marcus’s Study). Upstairs Billy kills a Mimicry Marcus and takes the KEY ITEM Leech Capsule and MAP Laboratory Map, then opens a path for Rebecca.
6
Send the Leech Capsule down to Rebecca, who gathers the Red and Green Chemicals. PUZZLE Chemistry: Red + Green = Stripping Agent; Stripping Agent + Leech Capsule = KEY ITEM Blue Leech Charm. Send it up to Billy.
7
Billy uses the Blue Leech Charm on the blue-marked door; inside, search the left wall for the KEY ITEM Input Reg. Coil, and take the KEY ITEM Green Leech Charm from the statue’s hand. Send the Green Charm to Rebecca.
8
Rebecca uses the Green Leech Charm on the operating-room door; grab the KEY ITEM Sterilizing Agent inside and use it on the gas-chamber panel to clear the toxic gas → KEY ITEM Breeding Room Key.
9
Lab files: FILE #22 Leech Growth Records (Leech Laboratory — holds the dial hint 4863), FILE #23 Laboratory Manager’s Diary (Leech Room), FILE #24 Investigator’s Report (Operating Room). Open the Breeding Room, fight the lizards and take the Dial — and don’t miss FILE #25 B.O.W. Report on the floor among the NE cages (easily overlooked).
10
PUZZLE Cable-car dial: send the Dial to Billy and enter 4863 (hint from Leech Growth Records) to open the cable-car door.
11
In the cable-car area collect the KEY ITEM Output Reg. Coil; give the Hookshot to Rebecca to swing up into the control room; install both the Input + Output Reg. Coils to power the car. Save.
12
Rebecca takes the WEAPON Magnum from the dead soldier in the cable-car cart — keep it on her for the next boss. Both board; Billy is knocked off and Rebecca goes on alone (re-seat the dislodged Output Coil and clear a Mimicry Marcus to get moving).
Chapter 4 of 6
AREA 4Factorythe underground works (Rebecca alone)
1
Arrive by cable car; grab Magnum rounds from the cart and the MAP Factory Map. Sweep the arrival rooms for herbs and ammo.
2
Cross the catwalks (dodge the two lizards) to find the KEY ITEM UP Key.
3
PUZZLE Turntable: use the UP Key at the panel to raise the turntable, cross, then lower it to descend; take the KEY ITEM Elevator Key below.
4
BOSS Proto-Tyrant (first encounter): Rebecca fights alone with the Magnum — keep distance, fire a few rounds then reposition (dodge its claw charge). It’s driven off, not yet killed. (See Bosses tab.)
5
Use the Elevator Key to power the elevator. It serves LV1 (Facility) / LV2 (Factory) / LV4 (Treatment Plant) — consolidate dropped supplies, then ride to LV4 for the finale.
Chapter 5 of 6
AREA 5Treatment Plant — FINALEthe water facility
1
PUZZLE Power grid (Control Room): press three buttons so every point lights — row 6 / column 2, then row 2 / column 2, then row 6 / column 3. Take the elevator down and save.
2
BOSS Kill the Mimicry Marcus in the corridor and grab the MAP Treatment Plant Map. Reunite with Billy — co-op resumes.
3
PUZZLE Crate & water bridge: Billy pushes the wooden/steel crates while Rebecca rotates the machine and floods the pool to float a bridge; cross for the KEY ITEM Handle.
4
Files: FILE #26 Investigator’s Report 2 (Generator Room, on a body) and FILE #27 Treatment Plant Manager’s Diary (Cargo Control Room floor). Open the Handle door and start the chemistry with the Red Chemical.
5
Save at the Lodgings (the finale’s main save room) — FILE #28 About Battery Fluid is on the SE bunk.
6
BOSS Proto-Tyrant (second encounter): both characters — control Billy up front and pour in Magnum + Grenade Launcher; this time it’s killed. Take the KEY ITEM Motherboard and install it to power the Gondola.
7
Ride the gondola: close the floodgate, then gather Industrial Water and the Blue Chemical. PUZZLE Chemistry: Blue + Red = Sulfuric Acid; + Industrial Water = Battery Fluid; + Empty Battery = KEY ITEM Hi-Power Battery (Billy boosts Rebecca to the Empty Battery on the ledge).
8
Power the Forklift with the Hi-Power Battery to raise the container and expose the KEY ITEM Keycard. Return to the Lodgings, save, and fully kit both characters (Magnum, Grenade Launcher, Shotgun, herbs).
9
BOSS Use the Keycard → Queen Leech (Phase 1, Marcus form): both characters — stay mobile, dodge the acid spit and pour in Magnum rounds. Afterward pick up KEY ITEM Shaft Key (L) and KEY ITEM Shaft Key (R) and use them on the two locks.
10
BOSS FILE #29 Gate Operation Manual is given to Billy automatically before the final room. Queen Leech (Final): it’s immune to gunfire — set Rebecca to open the ceiling shutters at the valves while Billy shoots to hold its attention; when sunlight floods in, it’s destroyed. The lab self-destructs and the game ends at dawn.
Completing the game unlocks Leech Hunter and (HD Remaster) Wesker Mode, plus rank rewards — see the Unlockables tab.
Chapter 6 of 6

Puzzles & Codes — Every Solution

Only two puzzles are randomized: the train brakes and the conference-room terminal code. They are re-rolled every playthrough, so read your own numbers. Every other code below is fixed and identical on Easy, Normal and Hard.
PuzzleAreaAnswer / CodeHow to Solve
Train BrakesEcliptic ExpressRandomizedTwo panels (rear balcony + driver’s cabin), activated with the Magnetic Card. Each shows a target number; press ten digits (1–9) that add up to it. Fastest way: press as many 9s as fit, then fill the remainder — e.g. target 67 = seven 9s (63) then 2+1+1. The cabin screen is broken, so track that one yourself.
ClockTraining Facility 3F8:15Mount the Iron Needle, then turn the minute hand to III (15) and the hour hand to VIII (8) and confirm. Opens the two clock-marked doors. The hint is in Notice to All Staff.
Conference DesksTraining Facility 2FRandomizedProject Microfilm A + B to get the desk chart, insert the MO Disk in the terminal to read a two-character code, then set both characters to solo, stand one at each coded desk and press together. Opens the armored doors.
Chess BoardMarcus’s Office 2FMatch the reference boardMove only the piece that is out of place so the big board matches the small board on the desk. A wrong move releases poison gas; leaving the room resets it. Reward: Book of Evil → Black Wing.
Statues of Good & EvilMain HallBoth statues on the scalesAngel Wings + White Statue = Statue of Good and Black Wing + Black Statue = Statue of Evil. Place both on the scales — the basement staircase opens under the painting.
Power RegulatorFacility BasementUP · UP · DOWN · UP · UPSets the needle to 70 and restores power. The target is stated in the About the Power Regulator file.
Animal TorchesFacility BasementDeer → Wolf → Horse → Tiger → Snake → EagleLight the animal statues weakest to strongest with the fuelled Lighter (Lighter Fluid comes from the kitchen behind the Fire Key door). Opens the blocked passage.
PianoFacility Bar 2FBilly plays it — twiceBilly plays to slide the wall open; send Rebecca in for the Battery (plus Magnum ammo and empty bottles), then Billy plays again to reopen the door so she can get out.
Duralumin CaseFacility Basement B3385Inside the locker opened with the Locker Key. Examine the case to read the code, enter 385Handgun Parts → combine with a handgun for the Custom Handgun.
Three TabletsObservatory 3FUnity + Obedience + DisciplineUnity from the bunk-room fireplace, Obedience from the vise (needs the Vice Handle), Discipline from the front-yard column (Battery-powered lift + Billy pushes a crate). Slot all three to lower the tower to the Laboratory.
Cable-Car DialLaboratory4863Take the Dial to the Machine Room lock and enter 4-8-6-3. The hint is in the Leech Growth Records file.
Factory TurntableFactoryUP Key — raise, cross, lowerUse the UP Key at the control panel to raise the turntable, cross it, then lower it to reach the level below and the Elevator Key.
Power GridTreatment PlantRow 6 / Col 2 → Row 2 / Col 2 → Row 6 / Col 3Three presses light every point (each button also lights the points two spaces away). Restores power and opens the way down.
Crate & Water BridgeTreatment PlantBilly pushes — Rebecca rotates & floodsBilly shifts the wooden and steel crates while Rebecca turns the machine between pushes; finally Rebecca runs the fill device so the wooden crates float into a bridge. Cross for the Handle.

Combinations & Chemical Recipes

Everything you build in the game, in the order you unlock it. Only Rebecca can mix chemicals and herbs — she carries the Mixing Set.

You GetRecipeWhat It’s For
Lighter (fuelled)Empty Lighter + Lighter FluidLights the animal-statue torches
Custom HandgunHandgun + Handgun PartsStronger sidearm — parts from the Duralumin Case (385)
Molotov CocktailEmpty Bottle + GasolineThe free anti-leech weapon — use these instead of Flame rounds
Stripping AgentGreen Chemical + Red ChemicalDissolves the Leech Capsule
Blue Leech CharmStripping Agent + Leech CapsuleOpens the blue leech-marked door in the Laboratory
Sulfuric AcidBlue Chemical + Red ChemicalFirst step of the battery chain
Battery FluidSulfuric Acid + Industrial WaterFills the Empty Battery
Hi-Power BatteryBattery Fluid + Empty BatteryPowers the Forklift → exposes the Keycard

Key Items — What Opens What

Key ItemWhere / Use
Mixing SetRebecca’s starting kit — combines chemicals and herbs
HookshotTrain balcony — grapples across gaps (roofs, church roof, leech room)
Gold / Silver Ring → BriefcaseTrain — both rings open the Briefcase for the Blue Keycard
Blue Keycard / Magnetic CardTrain — driver’s cabin access; brake sequence
Crank / Vice Handle, Handle, Panel OpenerOperate lifts, vises, vents and machinery
Facility / Fire / Water KeyTraining-facility & basement doors
Angel Wings + Black Wing / StatuesBuild the two statues to open the basement
Leech Capsule → Leech CharmLab — opens leech-marked doors
Input / Output Reg. CoilLab — power the cable car
Battery / Empty → Hi-Power BatteryFacility lift; treatment-plant forklift
MotherboardTreatment Plant — powers the gondola
Shaft Key (L) & (R)Finale — the two locks before the Queen Leech

Enemies — Threat & Counter

Fire is the recurring answer to anything leech-based — kill those with Molotovs or Flame rounds, or they burst back into a swarm. Everything else is a judgement call between the ammo it costs and the damage it deals.

EnemyThreatHow to Handle It
ZombieLow — run pastInfected passengers and staff. Learn the step-back dodge and walk around them; a close-range Shotgun blast aimed up can decapitate for an instant kill when you must fight.
Cerberus (Dog)LowFast infected Dobermans that leap. Cheap to kill — a few handgun rounds each. Shoot them mid-jump or keep spacing so they cannot pin you.
CrowLow — run pastSwarm and peck at the head. They cost more ammo than they are worth; just keep moving.
Leech / Leech SwarmLow — use fireIndividual leeches that reproduce and merge. Burn them or stomp them; the danger is only in letting them pile up.
Mimicry MarcusHigh — never shoot itLeeches merged into a humanoid. Bullets are wasted on it — only fire kills it. Use a Molotov, or simply sprint past. It also only takes damage before and after its transformation animation.
Plague CrawlerMediumA large mutated centipede that closes fast and hits with little warning. Control Billy and shoot down at it; flame weapons work well. (Not the Centurion boss.)
Giant SpiderMedium — skipWall-crawling spiders that spit venom. Shoot them while they are still on the ceiling, or walk past. Carry a Blue Herb or Green Chemical for the poison.
EliminatorMedium — avoid in the openInfected apes: extremely fast, bounce off walls and attack in groups. Fight them one at a time in a doorway if forced, otherwise outrun them.
HunterHigh — kill only if forcedReptilian B.O.W. that leaps and can decapitate a wounded character. The efficient answer is one Acid grenade plus a pistol shot; killing one with handgun rounds alone wastes a huge amount of ammo.
Lurker (Giant Frog)Very High — do not gambleIts tongue can swallow you for a near-instant kill. This is the one enemy where conserving ammo is the wrong instinct — use your strongest weapon immediately, or zig-zag out of range.
Infected BatsLowSwarm around the church and lab. The Shotgun’s spread clears several at once; you can ignore the small ones entirely during the boss fight.

Bosses at a Glance

BossAreaWho FightsBest WeaponKey Point
1. StingerEcliptic ExpressBillyHunting Gun / knifeBack to the doorway, aim down at the head. Drops the Panel Opener.
2. CenturionFacility BasementBilly aloneShotgun / Grenade LauncherShoot the white underbelly when it rears up. Rebecca is captured — be quick.
3. Infected BatChurchBillyGrenade LauncherAim up; about five rounds stun-lock it to death. Ignore the small bats.
4. Proto-TyrantFactoryRebecca aloneMagnumThe hardest fight on Hard. Keep moving, fire on clean angles only. Driven off, not killed.
5. Proto-TyrantTreatment PlantBothMagnum + Grenade LauncherBilly tanks in front. Killed for good this time.
6. Queen LeechTreatment PlantBothMagnumStay mobile, dodge the acid spit and the grab. Heal immediately after a grab.
7. Queen Leech (final)Treatment PlantBothSunlight — not gunsImmune to gunfire. Billy shoots only to hold its attention while Rebecca opens the shutters.

Bosses — Full Strategy

BOSS 1 Stinger (Giant Scorpion) — Train[+]
Where
Ecliptic Express bar/dining car, early. Billy fights (Rebecca is separated).
Kill it
Put your back to the rear wall to limit its pincer reach, aim slightly down at the exposed head, and keep firing the Hunting Gun while healing. It has low HP — just avoid its flailing death throes.
BOSS 2 Centurion (Giant Centipede) — Facility Basement[+]
Where
Breeding-pool / cage room. Billy fights alone — Rebecca is captured and her health drains on a timer.
Kill it
This is a race: free Rebecca fast. Circle-strafe the arena, target the belly when it rears up, and unload the Shotgun / Grenade Launcher. If you’re slow, Rebecca dies.
BOSS 3 Infected Bat — Church[+]
Where
The chapel/church, between the Training Facility and the Laboratory. Fight as Billy (higher defense).
Kill it
Stand near the altar with your back to a wall to avoid the lift-and-drop grab. Snap-aim up and fire the Shotgun — its spread hits the boss and the summoned bats together. The Grenade Launcher is hard to land on a fast aerial target.
BOSS 4 Proto-Tyrant (First Encounter) — Factory[+]
Where
Right after the cable car. Rebecca fights alone with the Magnum from the cart.
Kill it
Kite it — keep moving, don’t over-aim (it closes fast), and fire the Magnum (~6 shots) when you have a clean angle. Heal immediately after its knock-down swipes; never let it corner you.
BOSS 5 Proto-Tyrant (Second Encounter) — Treatment Plant[+]
Where
Lower treatment room. Both characters.
Kill it
Tag-team: position one character behind it while both fire — with two shooters (Magnum / Grenade Launcher / Shotgun) it goes down quickly. Last time you see it.
BOSS 6 Queen Leech — Phase 1[+]
Where
Treatment-plant battle room. Both characters; extra Magnum ammo is stocked here.
Kill it
Sidestep its arcing acid spit and melee lunges, pour in Magnum rounds, and heal as needed to force it into its final form.
BOSS 7 Queen Leech — Final Phase[+]
Where
Upper arena at dawn. It cannot be killed by gunfire alone.
Kill it
Set Rebecca to Idle/Solo and control Billy. Keep shooting the Queen Leech (Magnum) to draw its lunges away while Rebecca opens the shutters. When sunlight floods in, its UV weakness ends the fight. The lab self-destructs.

Weapons & Ammo

WeaponAmmoWhere / Notes
Combat KnifeBilly starts with one; a second is in cabin 202. Last resort.
Handgun (x2)Handgun BulletsRebecca & Billy start with one each. Billy’s is slightly stronger.
Custom HandgunHandgun BulletsBase handgun + Handgun Parts (Duralumin Case, code 385). Faster follow-up shots.
Hunting GunShotgun ShellsTrain cabin 101. Break-action, holds 2 — the weaker shotgun. (Infinite at Leech Hunter C-rank.)
ShotgunShotgun ShellsFacility statue room. Holds 7; angle up for grouped headshots. The crowd-control workhorse.
Grenade LauncherGrenade / Flame / Acid roundsPast the centipede area. Flame rounds shred leech enemies; Acid for certain bosses.
MagnumMagnum RoundsBody in the lab cable-car cart. Strongest standard gun — save it for the Tyrants and Queen Leech.
Molotov CocktailthrownCraft from an empty Glass Bottle + Gasoline. Great vs. leeches.
Sub-Machine Gun% ammoUnlockable — A rank (clear under 5:00). Added to Billy on later runs.
Rocket LauncherinfiniteUnlockable — S rank (clear under 3:30). One-hit kills but slows you down.
Magnum RevolverMagnum RoundsLeech Hunter B-rank reward — then hidden on the train.
Resident Evil 0 has no minigun and no separate ‘Samurai Edge’ unlock — the starting handgun is merely modeled on it.

Files (29) — “Fileophile”

Read all 29 files in a single playthrough for the completion reward. Files cannot be collected after you leave an area, so read each as you pass it.

The only files you can permanently miss are on the Ecliptic Express — once the train crashes you can never go back. Grab every train file (the five marked MISSABLE above) before you solve the brakes. Every later area allows enough backtracking that its files are safe.
#FileLocation
1Player's Manual 1Ecliptic Express — automatic (opening tutorial)
2Court Order for Transportation MISSABLEEcliptic Express — wrecked transport at the start
3Passenger's Diary MISSABLEEcliptic Express — passenger cabin
4Investigation Orders MISSABLEEcliptic Express — save room
5Notice to Supervisors MISSABLEEcliptic Express — dining car
6Player's Manual 2Ecliptic Express — automatic
7Note from Conductor MISSABLEEcliptic Express — conductor's room floor
8Hookshot Operator's ManualEcliptic Express — automatic (with the Hookshot)
9Brake Operation ManualEcliptic Express — automatic (driver's cabin)
10Notice to All StaffTraining Facility 2F — crank-handle room (hints 8:15)
11Regulations for TraineesTraining Facility — conference room, 2F
12Assistant Director's DiaryTraining Facility — Iron Needle room
13A Verse of PoetryTraining Facility — Microfilm B room
14Microfilm ImageTraining Facility — automatic (after projecting the microfilms)
15First Investigation Unit NotesTraining Facility — infirmary bed (easily missed)
16Marcus' Diary 1Training Facility — automatic (after the chess puzzle)
17Correctional Institute Inmates ListTraining Facility basement — save room
18About the Power RegulatorTraining Facility basement — power-regulator room
19Management Trainee's DiaryTraining Facility basement — past the animal-statue gate
20Marcus' Diary 2Laboratory — library (by the typewriter)
21Old PhotographLaboratory — automatic (with the Input Reg. Coil)
22Leech Growth RecordsLaboratory — tank room (cable-car dial hint 4863)
23Laboratory Manager's DiaryLaboratory — leech-zombie room
24Investigator's ReportLaboratory — tank room
25B.O.W. ReportLaboratory — Hunter room floor (easily missed)
26Investigator's Report 2Treatment Plant — balcony level
27Treatment Plant Manager's DiaryTreatment Plant — motherboard / gondola room
28About Battery FluidTreatment Plant — beds/typewriter room
29Gate Operation ManualTreatment Plant — automatic (final boss room)

Unlockables & Extras

UnlockableHow to Get ItDetails
Leech HunterClear the game once (any difficulty)Bonus minigame. Collect 100 Leech Charms (50 blue for Billy, 50 green for Rebecca) and get both characters out of the front door. Launch it from a Normal or Hard save — the rewards lock to that save’s difficulty.
Infinite ammo (all weapons)Leech Hunter — 100 charmsRank A in the minigame. The lower bands give: 90–99 Magnum Revolver, 60–89 infinite Hunting Gun, 30–59 infinite handgun, 0–29 Sub-Machine Gun ammo.
Infinite Rocket LauncherS rank — clear under 3:30Appears in Rebecca’s inventory on the next new game. One-hit kills, but it slows you down.
Infinite Sub-Machine GunA rank — clear under 5:00Appears in Billy’s inventory on the next new game. An S rank grants this as well.
Wesker ModeClear the game onceHD Remaster and Switch only — it does not exist on GameCube. Wesker replaces Billy with a Shadow Dash and an ammo-free Death Stare, and he can mix herbs. Locked to Normal and awards no rank.
Team Wesker costumeFinish Wesker ModeUnlocks Rebecca’s Team Wesker outfit for the main campaign.
Closet Key / costumesClear on Normal or HardThe key appears in cabin 101 on a replay and opens the alternate outfits for Rebecca and Billy. The HD Remaster adds further default and paid DLC costumes.
Ranks are awarded on Normal and Hard only and depend on clear time alone — saving, retrying and using unlocked infinite-ammo weapons do not lower them. The efficient route is: clear Normal → Leech Hunter on that same save for infinite ammo → use it for a sub-3:30 run. Full detail in the Difficulties tab.

100% Checklist

Finish the campaign (Ecliptic Express → Facility → Lab → Factory → Treatment Plant).
Read all 29 files in one run for “Fileophile” (grab every Ecliptic Express file before the train crashes — those are the only missable ones).
Build the Custom Handgun (Duralumin Case, code 385).
Clear Leech Hunter with 100 charms for infinite ammo on all weapons — launch it from a Normal or Hard save, never Easy.
Clear on Normal/Hard in under 5:00 (A rank) for the Sub-Machine Gun.
Clear in under 3:30 (S rank) for the infinite Rocket Launcher.
HD Remaster: clear the game, then finish Wesker Mode (unlocks Rebecca’s Team Wesker costume).
Unlock the alternate costumes.