Instructions
Locate the vent at the end of the walkway and climb inside. Follow the lights as you make your way through the ventilation system to the bathroom. Drop down and attack the man in the stall.
Leave the restroom and watch for the man on the other side of the window. Eliminate him by shooting through the glass or moving through the door to attack him from behind. Take the other door in the area to find a room with two engineers, two guards and a technician. Shoot the technician first, then shoot the guards when you get a clean view. Take out the engineers and proceed through the door.
Listen to the message from Trevelyan and enter the office on your right side. Attack the man in the chair, then navigate through the vent to reach the other office. Open the Weapons Crate here if you wish. Pry open the grate and eliminate the man by the terminal. Shoot the camera, then the technician. Leave the office.
Break the small lock on the door to access a maintenance room. Climb through the vent and open the gate. When the guards leave, shoot the camera and take out the pair of technicians. Enter the office and locate the blueprints. Take a photograph, then leave the room.
Move down the stairs and through the doors. Take out the technician in the structure ahead, shoot the camera and go downstairs. Eliminate the guard on the rail, then shoot the guard emerging from the door on the left. Sneak by the soldiers to the other end of the room. Subdue the man on the rails and head up the stairs. Shoot the technician and the camera, then return to the pair of guards. Blast the barrel to defeat them both, then take the catwalk to the next door.
Defeat the technicians and shoot the cameras in this room, then go upstairs and through the doors. Take out the guards, then force the scientist to deactivate the lockdown. Knock him out after he complies. Snipe the patrolling guards outside, then jump to the catwalk and through the gate.
Proceed down the hallways to the open room. Eliminate the guards below and up ahead. Go through the side door and move up the stairs. Shoot the camera and the technicians, then snap a photograph of the Sentry Gun blueprints. Backtrack down the stairs and head through the gate to the laboratory.
Eliminate all four enemies in this area and press the button by the blue screen. Move ahead to the next area of the lab. Access your Smart Phone and activate the alarm to clear out the scientists. Proceed through the doors and down the hallways to reunite with Trevelyan. Enter the next room to find the fuel tanks.
Clear the room of enemies and cameras. Plant a charge on each fuel tank, using your radar as a guide. Exit when you're finished and proceed quickly to the hallways. Move through the corridor to trigger a cut-scene that will end the level.