Jillian (Charlize Theron) is, as the title suggests, married to an astronaut, Spencer (Johnny Depp). While on a trip to space, he and his coworker Alex (Tom Noonan) are repairing their shuttle and there’s an explosion, causing them to lose contact with NASA. Upon returning home, Alex soon dies. While Spencer is physically fine, he seems changed by his experience. He is offered a corporate job and jumps at the chance to stay out of space. Shortly after, Jillian discovers she’s pregnant with twins. Her suspicions about Spencer are compounded by NASA employee Reese (Joe Morton), who tells her Spencer is now an alien that basically erased her husband like a cassette (or some other technical device invented after 1999). Jillian is left to wonder who the father of the babies is.
Something interesting in the film is the settings and minor characters, which symbolize the deterioration of Spencer and Jillian’s relationship. When Jillian and Spencer live in Florida, their house is big but homey, with lots of natural lighting. The co-workers at their going-away party seem friendly and likable. Jillian, a second grade teacher, works in an informal setting, sitting among her students. In contrast, the new house is overly big, sterile, and when it’s not dark, it’s lit with an ominous bluish light. (Actually, all of the settings are dark after Spencer comes home, even the going-away party.) The welcoming party she and Spencer attend is full of phony, snobby people; even the kindly woman Jillian befriends is spoiled, pointing out the bracelet her husband bought her when she had a miscarriage. Jillian’s new teaching atmosphere is now a formal private school, where the children wear uniforms and sit in neat rows.
Jillian sports a haircut very similar to that of Rosemary in Rosemary’s Baby, which is surely done on purpose since the films are similar in their themes of paranoia, supernatural babies, and untrustworthy husbands. 
Though the movie is a bit science fiction-y, I’d say it’s more classifiable as a horror movie. There are a few creepy moments, like when Alex starts displaying signs something is amiss—the viewer has no idea what will happen next. It reminds me of the Black Oil episodes of The X-Files, which are profoundly disturbing. Or Reese confronting Jillian about Spencer: “Can you swear to me that he’s still your husband?” The filmmakers do a marvelous job of building tension, and it’s unpredictable. Give it a look if you’re in the mood for a serious tale of alien activity.
