His latest patient, however, who goes by the name Prot (KEVIN SPACEY), is the most intriguing. Claiming to be from K-PAX, a distant planet some one thousand light years away, the otherwise human looking man doesn't seem to be affected by normal medication and reportedly can see otherwise invisible ultraviolet light.

Noticing that Prot seems to walk the walk and talk the talk of a convincing alien, Mark tries to figure out what would cause such an elaborate delusional state. As the doctor tries probing Prot for answers, he must put up with the patient's amused responses, as well as doubts from his associates, including Claudia Villars (ALFRE WOODARD), about his early diagnosis and plan for further investigation.

With the doctor and patient getting to know each other better from their various interchanges - including that regarding Mark's estranged son, Michael (AARON PAUL), from his first marriage -- Prot buoys the other patients' spirits by his announcement that he'll take one of them back to K-PAX with him upon his departure.

As Mark's continued detective work puts a strain on his marriage to wife Rachel (MARY McCORMACK) who cares for their kids Natalie (TESS McCARTHY) and Gabby (NATASHA DORFHUBER), he races against time and Prot's announced departure schedule to figure out if he's simply delusional or really is a visiting alien from another planet.

While that's something that parents and teachers alike seem to enjoy telling their kids or young charges, it seems that some filmmakers never received that advice growing up. Some try to make films that are both artsy and commercial - which, while possible, is extremely difficult to pull off - while others enjoy leaving viewers with nebulous endings that could come off either way, such as occurred in "Basic Instinct."

This week's example is "K-PAX," the tale of a psychiatrist trying to determine whether a recently admitted mental patient is simply delusional, or perhaps really is just visiting from a distant planet as he so calmly insists.

Based on Gene Brewer's 1995 novel - that I'm not familiar with and thus can't compare how things unfold and are ultimately resolved - the film sets up the viewer to question the character's origins, both by the way he acts and speaks and the visual clues used to give us hints and/or simply throw us off course.

There's certainly nothing wrong with that method of storytelling as it makes the viewer actively think and gather clues, much like the psychiatrist treating the mental patient/alien. It's also somewhat fun how director Iain Softley ("The Wings of the Dove," "Hackers") and screenwriter Charles Leavitt ("The Mighty") manipulate the viewer into thinking and then wishing that the subject at hand - Prot - is really from another world, and then seemingly pull the rug out from under their feet.

Yet, the nebulous ending, where doubt and uncertainty are reintroduced to the mix, is apt to leave some/many viewers confused and/or angry that the truth isn't clearly revealed. Personally, I like the vague quality of it all, but it's hard to tell whether that's the filmmakers' original intention or simply a cop out designed to force the viewer to decide on the reality of the conclusion.

Up to that point and the subsequent rug pulling, however, the film is a rather enjoyable if derivative bit of escapist entertainment that's fueled by some good dialogue and engaging performances from the two leads, Kevin Spacey ("Pay It Forward," "American Beauty") and Jeff Bridges ("The Contender," "Jagged Edge").

Essentially a psychological detective story mixed with mental institution elements from previous pictures such as "Awakenings" and "One Flew Over the Cuckoo's Nest," the film is best when Spacey's Prot amusedly responds to Bridges' character doing the inquisitive psychiatrist bit. Their interchanges are smarty, witty and well written, and the two talented actors play well off each other (with Bridges doing a one hundred and eighty degree turn after previously playing the alien visitor in "Starman").

Less successful, but certainly not horrible and obviously present as the film's "feel good" material are the moments where Prot interacts with the other mental patients and gives them hope while simultaneously causing some of them to cure themselves. The viewer manipulation factor feels a bit thick here at times, and it doesn't help that such moments come off feeling rather familiar. That said, I'm sure various viewers will find such moments satisfying and/or entertaining, at least to some degree.

Least satisfying - at least from a wishful perspective - are the deeper psychoanalytic scenes where we learn the truth - or at least what we think is that - about the character. I won't reveal the specifics -- or the particular films, their characters and behavioral explanations that will obviously come to mind upon this film's big revelation -- but they definitely fall into the been there, seen that category, and aren't of the audience pleasing variety - even if they technically work.

Then there's the conclusion that yanks the viewer back to dead center in the "is he or isn't he" quandary, after toying with our expectations and conclusions throughout the film. From what I could gather, the story leaves us with two possible explanations regarding Spacey's character, although certain early clues seem to lean one way far more than the other.

It's not really the sort of finale that's apt to have viewer's debating the ending or the events leading up to it, but I found it somewhat satisfying in its nebulous quality and am glad it wasn't as disappointing as the less than satisfying explanatory conclusion in the somewhat similar "Phenomenon."

Beyond Bridges and Spacey, supporting performances are generally solid. While Mary McCormack ("The Big Tease," "Private Parts") doesn't get enough time to do much with her somewhat disgruntled wife character and Alfre Woodard ("Mumford," "Down in the Delta") and other performers inhabit characters that seem likely to have been fleshed out more in the novel, David Patrick Kelly ("Songcatcher," "Dreamscape"), Saul Williams ("One True Thing," "Slam") and Celia Weston ("Hearts in Atlantis," "Hanging Up") are all good as some of the mental patients Prot encounters.

While certain things don't seem to make sense until you really start to think about them - such as why Prot, if really an alien, would allow his valuable time on Earth to be wasted stuck in a psychiatric ward - and the film often feels a bit too manipulative and familiar to previous stories, it's relatively entertaining and certainly easy enough to sit through, particularly thanks to Bridges and Spacey's performances and interaction. Not perfect and certainly not original, "K-PAX" starts off rather well, but isn't quite as successful in its second half when things are resolved, or at least partially so. The film rates as a 6 out of 10.