Locate the missing Marines | Mission 1: Distress A: CM Guide
Last update: 11 May 2016
Wait until O'Neal opens the hangar door, and go through it. You can go the door on the right at once, but it's worth to take a look at the massacred body of Bishop.
Start exploring the empty rooms. From this point on, it pays off to use the flashlight, especially since you don't have to worry about batteries running out. As you go, the game will throw you hints about using the motion tracker. It's not mandatory; you'll be easily able to find your way without it. After checking out the locker room, go through the mess hall and the room with cryo chambers.
At the fork in the road, turn right. Approach the door pictured on the above screen. Interact with it to use the welding torch and unlock further passage. Go down the stairs and you'll enter the quarantine zone, which clearly suggests Xenomorph presence. Again, follow the linear path; on the way you'll stumble upon dead marines and alien eggs from which Facehuggers have already hatched.