East Wing, Basement & First Boss

With the Rhombus Key, head down the first-floor left hallway (six zombies — a Green Herb sits by some vending machines here too). Take the door on the right into the observation room (careful, a Licker hangs from the ceiling — walk instead of running to avoid waking it, and grab the Handgun ammo on the left shelf). Outside, grab a Red Herb, then use the Rhombus Key on the metal door into the interrogation room for the Tower plug. There's a First Aid Spray on the table too, but taking it lets a Licker crash through the mirror.

Use the Rhombus Key on the records room door and check the lockers for Film B and Shotgun ammo. Continue into the west office — five zombies, one of them Officer Marvin Branagh if Claire didn't already put him down in her own playthrough. Clear them, grab the Green Herb by the door, and take the Heart Key from the small office along with a Small Key near the lockers.

With the Heart Key, head to the east office corridor and open the locked door with it (consumed on use). Clear the five zombies down the hallway (two Green Herbs on the floor), then use the power panel puzzle in the first basement room, same combination as Claire's:

This turns the weapons vault's card reader from red to green. The left hallway leads to a storage room with a typewriter and chest (a Red Herb is in the passage with two zombie dogs nearby, optional). Take the right hallway into the underground parking garage — a scene introduces Ada Wong, who asks for help pushing a truck out of the way. Grab the Green Herb here, push the truck with her, and go through the hidden door it reveals.

Grab Film C on a table, then take the left door into the cells — a Green and Blue Herb in the first cell. In the next cell, a scene introduces Ben Bertolucci; Ada arrives too, but a creature's scream interrupts them and she disappears again. Take the Lever from the shelf. Through the middle door is the kennel (two caged zombie dogs — taking the Red Herb here provokes both). Use the Lever on the manhole cover, climb down into a tunnel with two giant spiders, and climb back up the far ladder into a hallway with a room holding a typewriter, Ink Ribbon, and a Blue Herb.

Take the three chess plugs you've found (Bishop, King, Tower) from your chest and use them on the control panel in the machine room down the left hallway — it still needs a fourth. Back in the hallway, Ada reappears and Leon helps her through a vent into the next passage, where she runs into the girl from before — the girl flees, dropping a pendant Ada picks up and keeps.

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Now controlling Ada, clear four zombies outside and take the elevator down (it's a dead end), then find the water tank room nearby — same box-pushing puzzle as Claire's: push the right box fully, climb across to push the center box right through the gap, then push the left box fully, and flood the tank at the panel to cross for the Clover Key. Head back the way you came — Ada tosses the key and ammo to Leon, then Claire radios in to say she's cleared the helicopter wreckage blocking the way.

Back as Leon, collect what Ada left and return to the basement hallway (two more zombies). Use the Clover Key on the morgue's double doors — two Lickers wait inside — then grab the Red Keycard from a shelf and use it on the weapons vault reader (green to blue).

With the Clover Key, check the rest room behind the main stairs (Ink Ribbon, a locker with Shotgun ammo, Magnum ammo on the nightstand, and the Watchman's Diary). Then use the Clover Key and Lighter on the door at the end of the interrogation hallway to reach the press room. Light the boiler with the Lighter and hit the numbered busts in order:

A Golden Wheel falls loose — grabbing it breaks through the wall, and the Tyrant charges in. Knock it down or grab the wheel and run (knocking it down here drops Shotgun ammo). It breaks through again as you leave the hallway — deal with it the same way (Handgun ammo this time).

Head to the fire hallway and through the newly cleared door into the chief's office (Chief's Diary on the armchair, Handgun ammo on the desk). Through the next door, flip a light switch in a dark room to reveal a Crank Handle in a chest and Secretary's Diary B on a table. The Tyrant corners you again in the corridor back — it's best knocked down here since the hallway is narrow (Magnum ammo). Take the Golden Wheel and Crank Handle to the library. Use the crank in the wall notch to lower the clock tower stairs, climb them, fit the wheel into the gears, and press the button — a metal wall opens for the Horse plug. You can also use a vent here to shortcut back to the cell block, where a scene shows Ben attacked; talk to him for the Chief's Mail File before he dies. Ada reappears, then vanishes again. Claire radios that she'll escape through the sewers. Return to the machine room with the plug panel.

Walking back into the machine room triggers a cutscene revealing the creature that killed Ben: William Birkin, infected with the G-Virus.

William Birkin (1st Mutation)

Keep your distance and hit him with the Shotgun or Magnum — the Magnum is more effective. Dodge his iron pipe swing; it can kill you instantly if it connects. After enough shots, he falls through the machinery below.

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Use the fourth and final plug (Horse) on the panel to open the door. Ada appears again and follows you through the metal hatch beyond.