“One Flew Into the Cuckoo’s Nest” might be a better title for this heavy-handed combination of whimsy, sentiment and false profundity from director Iain Softley; the only question is “One what?” The script, adapted by Charles Leavitt from a novel by Gene Brewer, concerns (as did Eliseo Subiela’s 1986 “Man Facing Southeast”) a fellow in a psychiatric hospital who claims to be a visitor from another planet (in this case one called K-PAX). Though his analyst is understandably skeptical at first, the patient exhibits a thoroughly foreign manner and inexplicable scientific knowledge. This being a Hollywood product, of course, he also has a highly beneficial effect on the other inmates of the asylum–all of them stock figures from Screenwriting 101, it seems (the Tennessee Williams-style recluse, an obsessive-compulsive nebbish, a guy who’s terrified of germs, a woman who won’t speak, a burly fellow who finds that everyone else smells bad)–and teaches his doctor to wake up from his workaholic ways and stop to smell the roses, especially as regards his family.

This is very formulaic stuff, and it bogs down badly in the second half, when the doctor tracks down what he believes to be his patient’s human past, partially through regression therapy involving hypnosis. The initial seventy minutes are ponderous and preachy, but there’s sufficient interest generated by the cast and director to keep the viewer intrigued. The remaining fifty, however, grow increasingly heavy-handed and cloying, and when they’re capped by a denouement that practically ushers in angelic choirs to appear uplifting while also doing backflips to remain ambiguous, the level of manipulation has become insufferable. The slender tale has been loaded down with so much Hollywood contrivance and phony piety that it collapses under the weight.

One can divert oneself, nonetheless, by concentrating on Kevin Spacey, who has a field day playing Prot (pronounced with a long “o,” note), the mysterious stranger who asserts that he’s an alien, appears to be able to discern light waves imperceptible to other humans, says he travels far faster than hyperdrive, and knows far more about distant constellations than he should. Strictly speaking, it’s not a very good performance; it’s just a succession of tricks and gimmicks, from the charming way Prot cocks his head to his precious voice modulation to the cute little walk he periodically adopts. (A scene in which he converses with a dog will undoubtedly draw sighs from all the canine-lovers in the audience, too.) Audiences will eat it up, though, and it’s understandable why Spacey should have chosen to seize the chance to show off. Only a curmudgeon would point out that in his earlier work (through “American Beauty”) the actor specialized in roles that radiated intelligence and edginess, but now (with “Pay It Forward” and this picture) he’s choosingthe sorts of parts that his old idol Jack Lemmon might have essayed on his off days. It may be fun to watch Spacey pull off this kind of thing, but watching him makes one yearn for the old Kevin to come back.

As the other half of what’s essentially a two-character effort, Jeff Bridges is disappointing. He did well playing a variant of Spacey’s character back in 1984’s “Starman,” but on the other side of the desk he’s simply dull. It’s not really the actor’s fault–as last year’s “The Contender,” in which he was practically the sole saving grace, showed, Bridges is still capable of energetic performances–but here the script offers him little to work with. He’s pretty much reduced to pushing papers around, smiling knowingly, and tossing his glasses down in frustration from time to time; and his one big scene, in which he visits the former home of a man he suspects was Prot in earlier life, the fact that he’s made to stumble upon one telling clue after another (each of them followed immediately by an overwrought flashback) destroys any emotional honesty it might have had. (The script also has an unfortunate tendency to have somebody offhandedly mouth a remark rendering all too explicit something that’s already been shown–a device which has the unfortunate result of treating the audience like a bunch of dumbbells.)

It’s this persistent lack of subtlety that’s the major flaw in Softley’s direction. In his last film, “The Wings of the Dove,” the young Englishman demonstrated considerable skill and grace in adapting James’ prose to the screen, but in the present instance he seems more interested in giving his film a gleaming, almost metallic surface–something that he and cinematographer John Mathieson achieve quite nicely, to be sure–than in anything else. He treats the leads too deferentially, giving them all too free a rein, and he fails to impose a proper rhythm on the many episodes. The result is fatal. “K-PAX” wants desperately to soar, but it stays resolutely earthbound; it aims to create a sense of wonder, but all a viewer will wonder after seeing it is how so many talented people could have been misled into participating in such a stilted cinematic exercise.