Human/alien procreation has finally succeeded, and the result is a ravishing hybrid named Sara. The only problem is, she's got no one to mate with – and she really, really wants to mate. Can a good-hearted scientist use his DNA know-how to save Sara's race? Maybe, but if the first two films in the series have taught us anything, it's that spawning in a Petri dish sort of takes the fun out of it.