Opposite it is a room witha phone. Bug it, and go back to the elevator to use it. Once you come out, turn right, and pick the lock on the door. take a picture of Davidov's letter in the very small room, and go back into the corridor. Enter the room on the left just beyond the elevator and punch out this guard. Bug the phone here, and return to the corridor again. Go through the door straight ahead, and punch out the guard. Go into the room further on and knock out the guard in here. Bug the last telephone and leave. Enter the last room, punch out the guard, and take a picture of the screen. Leave. You will see a figure standing facing the stairs. This is Davidov. go up to talk to him. He will leave, then a whole load of guards will come down the stairs, so shoot them with a gun. (if you have one of course-which you should.) Enter the small door to the right of the stairs. Turn right, unlock the door at the far end, and head into the garage. Kill all the guards there before killing Davidov. You will find lots of ammo and armour in the corner if you need it. Pick up Davidov's ID card once he is dead to complete the mission
Yes- this is my own work