An interesting idea that sets up plenty of dramatic tension and gives both actors a great vehicle for their talents – Spacey's understated, Bridges' the most underrated of his generation.

A wacko appears in New York claiming he's from another planet (K-PAX) and calling himself Prot. Put straight in a psycho ward under the care of the resident (Bridges), he exhibits strange talents that can only be explained if he is from outer space as he claims. What starts out as a fantasy is gradually grounded in reality as the doctor investigates the truth behind the stranger's origins.

The big letdown in the film is that too much is left unexplained. When he turns out to be quite terrestrial and quite deluded, it flies in the face of his other-worldy talents (explaining the gravitational anomaly in his home system to some dumbfounded astronomers, being able to see ultraviolet light).

Resolution of the mystery does satisfy, but the story is more about the effect Prot has on the other patients, and the doctor himself - culminating in the final scene when he reconciles with his estranged son.