Turn right to see a bright "Exit" sign. Make your way straight for it and go outside. Before doing that, however, pick a document folder in the security room on the right.
Outside, go straight ahead, then left by the fountain. The gardens hide another document folder (on the stairs to the right of the fountain). Find an outhouse and go inside. You'll find two batteries and a key. Backtrack to the garden entrance and turn left. You should see a grated door.
Use the key and move forward. Open another door on the corridor. You'll see the mysterious mist again, but don't worry about it. Leave the corridor and look for a ladder that will take you to the roof.
Go forward, jumping when needed. Luckily, no one is after you - except for the video camera battery, which needs to be on now. Eventually, you'll reach a ledge. Go across it looking down.
On the other side, take a run up and jump over to the other building, then drop down on the grass below, using the crates for help. Look around, then approach the other crates. Climb them up and face the grate. Look up to see a hole.
Get to the other side and press on despite the darkness. On the way you'll see several lunatics, but they won't pay any attention to you. Shortly afterwards, you'll see stairs on the right and will have to cross through the gate up.
Follow the road until it ends. Turn to the right and jump through the hole in the gate.
Now, be very careful, you're going to have to play hide and seek again. Move in the darkness, heading a little to the right from your starting position. You'll see heaps of wooden boxes that will take you up. Move right towards the ledge.
Go until the very end, and when you can't move anymore, jump down and keep running forward.
A while later you should see a light. As you start walking towards it, your old pal will show up. Take turn into the bright alley, crouch and crawl under the wall.