By Paul Clinton
CNN Reviewer

(CNN) -- Faith, science and tolerance are the topics explored in "K-Pax," one of the best films of the year, starring Kevin Spacey and Jeff Bridges.

It's worth noting that this has been a dismal year for movies so far, so the standards are quite low. But that said, this is a well-executed film that doesn't fit any of Hollywood's tried and true -- and tired -- formulas. It expects an intelligent audience, and allows viewers to come to their own conclusions.

Spacey stars as Prot, a mild-mannered man arrested in Grand Central Station after he's mistakenly thought to be involved in a mugging. When he calmly announces that the light on earth is much brighter than what he's used to on his home planet of K-Pax, he's sent to a psychiatrist at a local public hospital.

Prot's assigned to Dr. Mark Powell (Bridges), who thinks he's just another delusional patient who'll eventually respond to treatment and return to reality. But the mystery surrounding Prot is not that easily solved. In an extremely tranquil way, Prot explains to the doctor that he's here on Earth conducting a fact-finding mission, and that he plans on returning to K-Pax -- 1,000 light-years away -- in just a few weeks.

While the doctors struggle to explain Prot's non-human response to medication and to light, his fellow patients have no such concerns. They believe, one and all, that Prot is from another planet and they want to go back there with him when he returns. Chaos is threatened as the patients all rally around Prot.

If this is beginning to sound like a combination of "One Flew Over The Cuckoo's Nest" (1975), and "Starman" (1984), which also starred Bridges, you're on the right track.

Events get more complicated as Prot explains how he uses light to travel as he lectures a group of skeptical astronomers with information regarding the mapping of the universe -- information even they don't have.

Powell becomes consumed with this strange patient. It drives him mad that he can't solve this case using standard medical techniques. He begins to question: Could Prot really be who he says he is? Of course, if that's true, this man of science will have to question many of his most basic theories about life.

At one point Powell says to Prot, "What would you say if I were to tell you that I believe you're as human as I am?"

"I would say you're in need of a Thorazine drip, doctor," Prot replies.

As the date for Prot's return looms nearer, Powell begins a desperate race to find Prot's true identity -- to save him from the mental destruction that will surely result when he finds out he can't return because there is no K-Pax.

Of course, there's that other possibility. Prot could be exactly who he says he is, and the doctor, with all his scientific knowledge, could be wrong.

Based on a 1995 novel by Gene Brewer, "K-Pax" has been adapted for the screen by Charles Leavitt with excellent results. This whimsical story could have easily been ludicrous in less talented hands, but Leavitt has carefully engineered a plot that steers carefully along the thin line between sanity and insanity, logic and fantasy.

Spacey is without a doubt one of the greatest actors on this or any other planet. Without his abilities, this film could never have been made. His characterization of a man who goes against all conventional behavior simply because he believes in something when all others doubt him is brilliant. Think of Jimmy Stewart's remarkable performance in "Harvey" in 1950.

Once again, Spacey should dust off his tux, polish his dancing shoes and get ready for another date with Oscar -- if not for this film, then perhaps for the much anticipated "Shipping News" coming out in December.

Bridges is also outstanding in his performance as the frustrated psychiatrist trying to come to terms with the most confusing case he's ever handled. Prot makes him question everything in his life, both professional and personal, and the good doctor's inner conflict -- against Prot's inner calm -- makes for great dramatic tension.

Director Iain Softley ("Wings of the Dove," 1997) maintains a somewhat surreal atmosphere of muted lighting and soft colors that lend themselves well to this strange journey of discovery. His casting is perfect right down to every extra on the screen.

Inspirational and profoundly moving, "K-Pax" speaks of love and tolerance -- perfect messages for our times.

"K-Pax" opens nationwide on Friday and is rated "PG-13" with a running time of 84 minutes.