When the level starts off you'll be behind some barrels, usually with a civilian on the other site. Go to your right to get around the barrels, then kill the civilian. Turn left and start down the corridor. At the next left run past fairly quickly because there is a gunner behind a door that closes when you get too close. Turn left at the intersection and keep going until you see a ladder going up. Take this ladder and climb through the air duct to the end. Beware, occasionally a civilian is inside the air duct. Break the grate, and the pipes, and drop down. Go to your left and then through the door, then exit the next room. Go out straight and turn right. At the fork, turn left, and kill the android. Go up to the second level and destroy both sets of pipes to open the door on the opposite wall. Wait for the people inside to come after you, and kill them with stealth. Go through the door and to the left, be careful because it's another android behind a closing door, so make a run through. Break the panel next the door and go through. You have to be careful because some of the civilians are carrying flame throwers. Wait until their back is turned, then rush them. Go through the corridor on the left, and then turn left into the room there. Climb up the wall and onto the ceiling. Above the table is a grate you must break and go through. Do that to get into the pipes again. Follow those pipes to the end, get out, turn left. Break the panel next to the door to open it. Go straight across the room with the ladder and into the room on the opposite side, and into the vent on the left. Break the first grate on the left and keep going. Drop down into the cryo-sleep chamber and smash the panel next to the door. There may be androids behind these doors, so be cautious. Go through the door and follow the tunnel to the fork. Turn left and get to the first light. On your left you'll see a glass panel, break it and jump through. Straight through the room break the panel and feast on the civilian in the room, then go to the door to the right from the glass panel. Break the panel and turn right. Kill the two turrets there. (See why you went through the glass panel?) Now, go back to the left and follow the tunnel to the next fork. Take a left. Break the panel and open the door to another cryo-sleep chamber. Climb onto the ceiling and back through the vents. At the fork, turn right. Climb out, and look down to your left. You should see a security guard. Either rush him or go through the third pipe on the right to sneak around to his side. Then go open into the vent at the end of the hall. Climb up and follow this one to the end, and climb or jump down to the floor. Turn around and go through the corridor. Look to your right. There are some exploding barrels there with an armed civilian. Climb to the ceiling to pass the barrels and kill the civilian. Go through the door, turn left. Run straight ahead into the vent again. At the end of the vent and small room, turn right and break through that grate. Turn right and climb or jump down the tunnel. Walk ahead, look to your right. There's a pipe there, but it's covered. Remember where you are. Climb back up the tunnel and through the door on your right. Another room with stairs. Just go straight across the floor, and keep going straight. Follow the winding tunnel and you should see an area with a pipe above you. Jump up into the pipe and climb up. At the top break the panel next to the door and go through it. Go straight across this room to the other side, and break the panel to the left of the door. Go inside, break the next panel, and you're in the room with MOTHER, the computer. Break all the screens on the wall. You now are timed to get back to the covered pipe you saw earlier to exit. Go back out of the room, straight across, and down the pipe. Keep running straight ahead, and climb up the wall. Go straight through the room with the ladder, and go left down the shaft again. Go right, and through the now open pipe. At the end, turn left into the next pipe to end the mission