You leave into the corridor and go around the corner to the right. There is a closed passage and a place under the handle. Now you do not have it. Go to the other side of the corridor and see a falling helicopter. Go outside and go down. After the video, pick up the pliers from the shelf and cut the chain with them.
You will return to the eastern corridor, where you were at the beginning of the game (when you were looking for a notebook). Kill all the zombies or run around them. Find the door with the chain and cut it. Enter the eastern office, stab the second window to the left, or wait for the zombies. There are different things in the office, but the most important thing is the electrical part (fuse) and the valve. Take both items, move the chairs away from the door and return to the corridor. Go left to find closed shutters. There is a panel on the right. Use a fuse on it and return to the hall. Be sure to save.
Go to the west wing in the room from which you went out through the window, cut the chain on the door with cutters. After that, the pliers will not be needed (all unnecessary items are marked with a red tick). Go through the door and find an electronic gadget on one of the shelves. Take this opportunity to look into the arsenal and open a showcase with a shotgun.
Climb to the second floor, enter the shower, and apply the valve to the pipe to remove the steam. Follow forward, go out into the corridor and find Licker. Destroy it with a shotgun or silently go around. Enter the room to the left — S.T.A.R.S. There is a box on the table in the room to the left, and on it is a battery. Take it away; combine the gadget and the battery in your inventory to get a detonator. You can find other useful items as well as an arsenal with the revolver. To open it, you need a flash drive. The red stone is the first step towards achieving the goal.
You will need to find in the observation room of the east wing of the box with diamonds. This can be done later (we will indicate when).
There is a door to the laundry room at the end of the corridor where Licker was. It is closed, you need a key with a heart, but you only get it when playing for Claire. Open the last door to get into the room with the Unicorn. Return to the hall and save.
Follow to the third floor, to the place where the explosive is located (in front of the library). Use a detonator on it, stand back and wait for the explosion. Go to the statue of the women and set the characters as written in the notebook of the officer. Take the third locket, kill Licker or go around it. Return to the hall and place all three medallions on the statue. Go downstairs, follow the only route and the boss battle will begin. Shoot at the enemy until the yellow eye opens. Next you need to shoot at eye. The ammo are scattered around the arena.
Kill him, climb the stairs, find the control room and move the bridge. Get outside to be in the parking garage.
Look around, go to the lattice and study the terminal on the side. You need a key card. After the video, follow through the far door with a green lamp. Make your way through the isolator to find a living person in the far-room. After the video, take the handle from the table and return to the parking garage. Also in the insulator you need to lower the lever, located after the first room with the cameras.
This lever opens another door in the parking garage. Go through it, go right through the Kennel and look at the morgue. There are cameras on the right and left. Go to the left and open the second from left to right. Next to the corpse will be a key with a diamond. Take it and move on to the generator room. Here you will need to pick up the orange box. Inspect it in the inventory and get the first part of the device. Interact with the panel and lower the third and fourth toggle switches to open the door.