This movie is based on a video game that I have never played, so I can't comment on how the movie's plot follows the game.  When the movie starts, there is a really cool aspect to it.  A naked woman has just regained consciousness in her shower and can't remember anything.  The next few minutes are packed with action, and a team of military personnel take them to the Hive (an underground research lab).  Slowly each of them get filled in on the details of the mission.  What that mission is, you'll have to watch the movie (or e-mail me) for.