OR:
Weyland-Yutani have been lookin for the Yautja homeworld ever since they learned about the Yautja's existence. So far, the closest they've been to success was when Alpha Draconis attempted to board a Yautja Clanship, but that failed miserably.
With captured information from thier battles on Earth and capturing the Space Jockey Weapon (whatever the hell it is, tests are still ongoing), they have located a Yautja planet. Not a major one, but it is a step forward. Using thier contacts in the government, they were able to sneak a few agents aboard a USCM Cruiser, and arranged for it to crash-land on the planet.
Some of W-Y (the saboteurs) are still with the marines, feeding information back to the Company. They need to somehow get off-world, and gather as much information they can on other Yautja Worlds, as well as capture Predtech. The survival of the marines, is as always, a secondary goal.