If you still need help then are you on the burning house mission?
You have to make your way through the building until you come to a room where one of your contacts says 'He should be in here' or something like that. Then you run around to the other side of the flames and there should be a man lying on the floor. Talk to him then exit the room (not using the door you entered with) and approach the room opposite. Try to shoot out the skylight from as far away from the door as possible as the smoke reduces your health. Then once the room is clear of smoke enter and make your way to the door on the left. Through that door is the next level.