When a beautiful human-alien hybrid (Natasha Henstridge) escapes from observation, scientist Xavier Fitch (Ben Kingsley) dispatches a crew of experts to find her before she is able to fulfill her horrific purpose: to mate with unsuspecting men and produce offspring that could destroy mankind. As her deadly biological clock ticks rapidly, Fitch and his team (Michael Madsen, Alfred Molina, Forest Whitaker and Marg Helgenberger) are hurled into a desperate battle in which the fate of humanity itself hangs in the balance!