The Basement

• At the Basement Safe Room, grab the herbs, the Basement Map, and check the (largely useless) Inmate List. There's an Ink Ribbon here if you want to save.

• In the next room, boost Rebecca through a hole in the wall into a torture chamber. The exit door is locked — read the notes on the floor to learn you need to set the power regulator to 70. Flip the switches in this order:

  up, up, down, up, up
  

• With the regulator set, both Rebecca's exit and the spider hallway's second door open, and the Training Facility's boiler stops venting steam. Unfortunately, an eliminator ape corners Rebecca before you can celebrate.

• As Billy, check the room that just opened off the spider hallway for Handgun Ammo and Shotgun Ammo, then avoid the next door — a pack of eliminator apes waits behind it and can overwhelm you.
• Instead, backtrack to the Main Hall, through the Dining Room, and into the Boiler Room, grabbing herbs on the way down its stairs.
• The first room below is crowded with three eliminator apes — turn right immediately and sprint through rather than fighting your way across. You'll reach Rebecca just in time.
• Back outside that room, stand your ground in the narrow hall and fight the three eliminator apes properly — Molotov Cocktails for Rebecca, Shotgun for Billy, keeping your backs to the corner so they can only approach head-on. Grab the Handgun Ammo left behind and head north.

Another spider-lined hallway leads down to the Control Room — cross it the same way as before, one character at a time.

• Optionally, a side room off the spider hallway holds a Locker Key, guarded by two plague crawlers — worth the fight if you want the Custom Handgun later.

• In the Control Room, stock up on Handgun Ammo, Shotgun Ammo, and a hidden box of Magnum Rounds. If you have the Locker Key, unlock the small locker and open the Duralumin Case with the code below to get the Handgun Parts — combine them with either Handgun for a faster, stronger Custom Handgun.

  385
  

• Send Billy down to the Testing Chamber with the Grenade Launcher, Grenade Rounds, and a restorative item. From the Control Room, Rebecca operates the gates: hit Left, then Center to clear his first path, then Center again once he's through to raise the final gate.

• Grab the Water Key from the cage they were guarding.

• Back in the room where you fought the first three eliminator apes, examine the animal statues and light their torches with Billy's Lighter in this order:

Deer, Wolf, Stallion, Cougar, Serpent, Eagle

• This opens two doors. Grab the Empty Bottles and Unity Tablet from the first one before heading back toward the Main Hall.
• With the Water Key, head up to the Wet Room area and unlock the Water Motif door near where you found the Grenade Launcher.

• Send Rebecca alone through first. The first side room holds a Vise Handle guarded by a leech — grab it and run rather than engaging.
• Regroup, then push together into the next side room, where Billy can play a dusty piano to unlock a hidden door. Send Rebecca through for Magnum Rounds, Empty Bottles, and a Battery; the door shuts again once she has it, so play the piano a second time to free her.

• Hand Billy the Vise Handle. Solo, he pushes past the leech again into a hall with two doors: the northern one has two zombies and the Obedience Tablet, freed with the Vise Handle.
• Send Rebecca back out through the Water Motif door while Billy drops his gear (he's about to run an item-fetching errand) and follows through the western door for a room full of loot — Handgun Ammo, herbs, Aid Spray, and Empty Bottles.
• Regroup, retrieve everything you dropped, and head to the Main Hall's front door to reach the courtyard outside.
• Use the Battery on the lift in the eastern corner to lower a cargo box. Push it toward the center, position it under the tall pillar, and climb it to grab the Discipline Tablet.
• With all three Tablets — Unity, Obedience, and Discipline — head to the Wet Room stairs and push through the plague-crawler-infested walkway to the Observatory. Use the Tablets at the dais to unlock the way down and change your return route to the Laboratory.