Real estate developer Jake Berman hires private investigator and war veteran Jake Gittes for some run-of-the-mill matrimonial work. After Berman shoots his wife's lover, who happens to be his business partner, Gittes is drawn into a web of conspiracy and deceit involving the oil reserves beneath Los Angeles. While investigating, Gittes hears a voice from his past that causes him to revisit a traumatic case in Chinatown.

Trying to rescue her home planet from destruction, a gorgeous extraterrestrial named Celeste arrives on Earth and begins her scientific research. She woos quirky scientist Dr. Steve Mills, a widower with a young daughter. Before long, Celeste finds herself in love with Steve and her new life on Earth, where she experiences true intimacy for the first time. But when she loses sight of her mission, she begins to question where she belongs.