The police station
So, now you're in the precinct. Go to the door and enter the 5929 code, if I remember correctly. Enter CROUCHED. Very important.
You will see a guard slowly walk away from you. Stay crouched, and wait at the very border of the darkness. Do NOT let your meter go farther than the first line, or the guard might see you. Wait for him to come back.
When he finally came back, he will turn away. When he's not looking, walk, crouched, towards him. You will probably have to accelerate. DO SO.
When he'll hear you, you should theoricaly be in range to grab him. Do so and GHH him. Now, walk into his office, and take the data stick.
Crouch and walk toward the other big glass door. There should be a door on your left. If you do everything right, the guard in it will NEVER even know you're there. So don't even bother with it.
In the room with the big window, you can see someone with a laptop prancing around. Wait and see his timing. Enter the room when he's not looking, and hide behind the station in the middle of the room. When he's walking walk behind him and grab him. Interrogate him. He will tell you that the bodies in the morgue are the agents you're after. Tought noodles on ya.
hit and hide him.
Get in the morgue, and time yourself with the camera. Walk to the place, behind the plastic curtain, on your right. Wait there until the camera isn't looking at you.
Run under the camera. When it's looking away, run between the two cadavers, and come back. If you timed it right, you should have information about the two spooks, and notice that their subdermals have disappeared.
Now, exit the room the same way you came.
Keep following the hallway until you reach the final door.
Open it and go upstairs. The second door will lead to the precinct's entrance. Crouch and slow-walk, hugging the wall on your right (not putting your back on it). Go BEHIND the curtain. When you're finally at the door, the guard and the civvie should still be talking. raise your speed ONE notch and walk across the light. You should now be in total darkness. Just wait for the two guys to finish talking, and when they're done, slow down as much as possible and crouch your way to the entrance to the stairs.
Once in the staircase, just slowly walk your way up. You will reach a computer room. Slow-crouch your way behind the first guy, GHH him. Repeat for the second guy.
Do every door in sight. The farthest one contains bullets, in case you might need them. As I mentionned, in the whole mission I fired only once, so I hardly even cared for them.
The second room contains some guy that was interrogated. You can't do anything there. Don't bother.
Now, the room left has some guy behind plastic curtains watching at monitors. THIS is your mission objective. Enter the room, crouching and being as slow as possible, and GHH the poor soul.
Use the computer.
You now have to exit the building.
Go back down thru the stairway, and crouch-slow you way to the second door. Open it. The guard will see you. Just run AS FAST AS POSSIBLE outside, and you're cleared!
Good job!