Chris Walker will look for you so what you do is when he goes further to the right , you craw slowly towards the stairs and then run.
Once you're back on the ground floor, you'll need to circle this room from above, then escape through the grate-less passage on the left. Afterwards, turn left; another inactive chamber will be blocking the other path. Squeeze through the shelves. If the monster was still after you, he'll stop now. Ahead, by the corpse of the dead guard, you can find a battery, and on the right there's a collapsed passage you're going to have crawl through. Afterwards, follow the corridor until you reach the arena entrance where one the bad guys beheaded a man.
As you step onto the arena, everyone in the cages will turn their attention to you, but won't attack. On the left, there's a bed you can use to boost yourself up. Once there, go right.
You're going to have walk past a man sitting on a chair; middle through, he'll jump you, so move the mouse to shake him off. Keep going. Hug the wall at the collapsed floor segment, then jump across. The stairs up will lay open before you.Before you go up, though, grab a document folder from the nearby cell. There's nothing else beside it. On the next floor, turn right immediately to find a battery in a cell, or turn left to move the plot. As you follow the main corridor, one of the inmates will leave his cell and start hitting you if you're close. Keep going until you have to hug the wall again. If your pursuer hasn't given up yet, he'll leave now.As soon as you take a few steps, another hyperactive lunatic will start choking your character through the bars. Move the mouse until he lets go, then proceed ahead.Eventually, your character will step into an abandoned solitary. To the left, there's a small hole that you can squeeze through. At the other side of the wall you'll stumble upon a man who won't do you any harm. Leave his cell and follow the corridor to the right. In the last cell on this level you'll find a battery, and in the previous one, another hole down. There, go down the stairs that's located on the same side as the light.
On this level, in the room with a lot of blood, turn left. You'll find yourself in a large hall, with another hole in the center. Same as before, jump down.
Your new objective is to find a way out of the sewers. You'll find yourself in a some sort of sewer system. Keep going down and down, there's no other way anyway. To make things easier, you may want to switch to night vision. Eventually, you'll reach the actual sewer tunnel, with two paths to go, left or right.The path on the right is collapsed, so take the left, brighter one. As soon as you can, turn right and follow the tunnel until you reach a smaller sewer. Crawl through it.
Once you're in the second room, you'll get another objective - to turn two valves in order to unlock the next mission. After taking several steps you'll realize it's not going to be that easy, not with your old pal re-appearing and you having to move past him. If he detects you, either run towards the crack you used to get here and stop the chase altogether, or turn right and finish your first valve.
The second valve is in the room on the other side, so to the left from where you came. Also with a battery.
Naturally, now you need to get back to the beginning. Evade your pursuer and backtrack the way you came, then go down the ladder.
Move ahead until you find another ladder. Climb it up and look around. The path will lead to the right, and you will keep hearing the prisoners' screams. According to the sign, the path leads to the admin block.Keep going straight ahead until you see a door on your left. Go through it to meet with one of the inmates, but this one will be the first to talk some sense. On the right, there is a hole in the floor. Jump down to get to the next level.
In the lower sewers, turn left and move along the tunnel. Eventually, you'll reach a door on the left. Ignore it, approach the wall, crouch and crawl through the smaller tunnel.
Immediately afterwards you're going to have to jump back in the water. Look for the stairs; they should be somewhere around. Be ready to get wet again.
"Wading in water, turn left when you can, and crouch under the metal grating.
You'll be back in the old fashioned cell. When you leave it, you'll see a madman running straight towards you. If you try to turn back, it will turn out someone has closed door behind you - but the one you've been running from has now disappeared.