A mysterious man (Kevin Spacey) shows up in Grand Central Station claiming to be an alien, and is promptly taken to a mental institution.
When he doesn't respond to medication, he begins seeing a psychiatrist (Jeff Bridges) who is fascinated by him. The man calls himself Prot (rhymes with "boat"), and tells the doctor about life on his home planet, K-PAX.
When he learns of Prot's ability to see ultraviolet light, and his savant-like knowledge of astronomy, the psychiatrist, despite his skepticism, begins to believe.
But his continuing obsession with the man begins to bring out deeper issues, and Bridges' character is compelled to question whether his patient is a visitor from another world, or simply a deeply disturbed man.
Based on the novel of the same title by Gene Brewer, the film is directed by Iain Softley.
More than a science-fiction tale, K-PAX is a reflection on the way we live our lives, the things we think we know, and the connection of one human being to another.
Spacey gives his usual believable, complex performance, and Bridges is exceptional in the role of a man torn by what he knows and what he wants to believe.