In Aliens: Colonial Marines you get to play the part of Winter, a Marine on the ship Sephora responding to the rescue beacon that was sent out in the movie Aliens. You return to LV-426 17 weeks after the beacon was sent out. But during those 17 weeks, Weyland Yutani has been busy: They found the Sulaco, brought it back to LV-426 and have restarted their operations to capture and control the xenomorph. That is, as you know, easier said than done. Chaos ensues.