The game begins with you in the car. After a short cutscene showing how you reach the old, gloomy manor, your character picks up his briefcase and pulls out a message. Read it, press "Close" at the end, and wait for your character to leave the car.
The game will then tell you that to view the mission's objectives you need to press "Tab". To browse through the collected document, press "J", and to open the notebook, press "N".
As soon as you familiarize yourself with the tutorial, approach the gate and turn right. You'll see a gate; go through it. You'll be informed that every door can be opened either slow or fast.
Once you're in the courtyard, make your way toward the main entrance in front of you. If you look at the windows, you'll see someone's silhouette projected against the light of a lamp. Without delay, approach the main doors - only to find out they're closed.
Turn left and approach another gate, this time broken open at the bottom. Crouch as the game suggests and move through to the next area of the courtyard. There will be a door on the right, and a ladder leading to scaffolding on the left.
Approach it and climb the wooden structure. Turn right and shortly you'll reach a spot where you're going to have jump. Step back a little and leap across the hole. Keep climbing by pressing Space. Once you're up, turn around and walk along the building.
After a while, you'll find yourself under a window - jump up to it. Press Space and go inside. That's when the lights are going to go down, so activate the night vision function. To do it, press the left mouse button to turn the video camera on, then F to switch to night vision. Be careful, though, because night vision consumes the battery. Look around the room and walk through the door the step into the corridor.
Enter the next room. As you approach the table, the TV on the wall will turn on and start hissing. Turn around and get back out on the corridor.
Squeeze through the shelves and go inside the room on the left. You'll find a battery in the desk drawer and documents lying on top of another one. When you read them (or not), leave the room and continue along the corridor.
Enter the room at the end of the way, on the right, and get into the ventilation shaft. Crawl until you can jump down into a bright hall. Approach the door labeled as the library. Walk along the shelves until you reach an exit. Use the video camera.
Once you're through, keep going down along the corridor, past all the stuff that's there. At that point, you'll be thrown out the window. When the cutscene ends, look to the left and make your way to the computer lab.
There's nothing useful inside. Go back to the corridor and look to the right to find another document describing the state of one of the patients (lying in the darkness). Move out.
Eventually, you'll walk out into a corridor and see a man on wheelchair. Walk past him and into the door with several others like him. You don't need to sneak, they won't pay you any attention. Crawl under the closed door. From the corridor, enter the next room.
You'll find a corpse of a guard with an access card to the main door. Backtrack to the main hall, but watch out - one of the psychopaths you past by earlier won't be so calm this time.
Back in the main hall, approach the reception desk and take the documents. Make your way towards the elevators and turn right to a door removed off its hinges.
Step into the corridor and you'll see one of the enemies banging on the door at the end. In the first room on the right, you'll find a battery; there's also a bathroom on the left, but nothing to find in it except a dead body.
Keep going until you see a security room. Go inside, use the access card and interact with the keyboard. The power will go off in a minute, so hide in one of two lockers (I hid in the one on the right). Once the psycho enters and leaves, exit the room and head for the basement on the right.
Go down the stairs. If you squeeze through the crack in the wall, you'll find a document to the right. Go further to find a generator which will tell you to start the pumps.
Go past the generator and through the door on the right, by the stairs. You'll find the first pump, so start it and hide in a locker. In a second, one the enemies will come in and check one of the lockers (pray it's not yours), and then leave. When it's clear, move to the next room and start the second pump.
Be careful, one of the bat-wielders will be walking through these rooms. You can hide in lockers, but don't forget they can't see in the dark, so if you see one coming, slip into a corner and he won't detect you. Keep in mind, though, that the corner has to be very dark.
Once the two pumps are up and running, there will be only one indicator light to turn on left. From the main terminal, turn left and go towards the door on the wall in front of you. First, turn right when you can and take two batteries from the locker in the room.
Afterwards, follow the corridor, jumping through the desk standing in your way. There is another battery in the next room, so take it and get back on the track until you reach a fork in the road.
On the wall, there will be an arrow pointing you to the power station. Follow the direction, past another desk, and enter the last room. There will be two batteries and a lever there, which the priest had used earlier to turn the power on. Pull it back and backtrack to the indicator light.
If the bat-wielders start chasing you, remember your character can withstand only around four hits before going down. You may slip past the guy and make a run for the indicator light. Turn in on and backtrack to the ground floor.
Go back to the room from which you can open the main entrance and interact with the computer. Again, something will go wrong and you'll lose consciousness.