Writer-director Nicole Kassell delivers a quietly stunning debut with "The Woodsman," a movie that on paper doesn't immediately suggest a fun night out at the multiplex. The story of a pedophile who returns to his home town after 12 years in jail, this by turns unsettling and inspiring drama offers no easy answers, let alone identifiable heroes or villains.

"The Woodsman" is not to be missed, if only for an unforgettable leading performance by Kevin Bacon, who with luck will now be remembered not only as the punch line of the "Six Degrees" movie trivia game but as a serious, seriously good actor. Bacon seems to have acquired a few more skins to play Walter, a man so wary of his dark compulsions that he seeks to shield himself from the world, and vice versa. Terse, dead-eyed, moving like a ghost through his post-prison life, Walter is surely the most unlikely movie protagonist this year, but Bacon succeeds in making this otherwise repugnant figure someone filmgoers can root for.

That's a formidable task, and Bacon deserves heaps of praise simply for attempting it, let alone accomplishing it with such discipline and, finally, generosity. But "The Woodsman" succeeds even beyond this crucial central performance. In the surprisingly assured hands of Kassell -- who was a film student when she optioned Steven Fechter's play -- the movie is not only Bacon's finest hour but a potent ensemble piece, featuring equally strong turns by actors who deserve to be seen more often, among them Bacon's wife, Kyra Sedgwick, Benjamin Bratt, Mos Def and a young actress named Hannah Pilkes. Kassell has coaxed outstanding performances from each, while imbuing "The Woodsman" with a visual style all her own, one that combines a gritty realism appropriate to the subject matter with brief stop-action and slow-motion flourishes suggestive of the fairy-tale origins of its title.

Those tales are more often the stuff of nightmares than of dreams, of course, a fact Kassell and Fechter, who collaborated on the screenplay, never forget. On the outside, Walter's life is prosaic: He works at a lumberyard, drinks the occasional beer with his brother-in-law (Bratt) and has even started seeing a spirited young woman (Sedgwick). But his every step is haunted, not only by his past (which is never entirely spelled out), but by his uncertain future and whether he will succumb to his psychic demons again. As fate would have it, he has moved into an apartment across the street from a playground, which he broodingly observes from his living room window. When Sedgwick's character, Vickie -- a tough-talking forklift driver from work with a wounded past of her own -- asks him if it's a school and he quickly replies "K through six," his response seems creepily authentic.

Several questions, each with its own high stakes, animate "The Woodsman." Will Walter and Vickie's romance overcome his affliction? Will Walter reunite with his estranged sister? Will the police sergeant who's been dogging him -- a soft-spoken philosopher-gumshoe played by the always compelling Mos Def -- nick Walter for a series of nearby sex offenses? Or will a nosy clerk at the lumberyard succeed in forcing Walter off the job? Kassell ratchets up the drama as each of these story lines comes to its own unpredictable conclusion. But mostly, Walter -- and the audience -- care about only one thing: Will he relapse? "The Woodsman" offers up no platitudes, pieties or false hopes in response to that question. While Walter works through the issue with his therapist and silently with his own anguished psyche, Fechter and Kassell give filmgoers a firsthand glimpse of a sex offender who isn't a monster but a man, albeit one who is afflicted with a grievous obsession.

Inevitably, Walter -- and, by extension, the filmgoers who have come to care about him -- must face the reality of that obsession, and the scene in which he makes the pivotal choice of whether to give into it is the film's defining moment. Filmgoers will no doubt be holding their collective breath, waiting to see what Walter will or won't do, desperately hoping for him to go in one direction but not knowing until the last second whether he will. Like everything else about this haunting film, the scene is so understated, so perfectly calibrated, that it's easy to overlook the technical difficulty of pulling it off. Kassell doesn't just make it work; she makes it a small masterpiece.

The Woodsman (87 minutes, at Landmark E Street, Loews Georgetown and AFI Silver Theatre) is rated R for sexuality, disturbing scenes and profanity.

Kevin Bacon, left, plays a pedophile who clashes with his brother-in-law, played by Benjamin Bratt, in Nicole Kassell's "The Woodsman."Bacon succeeds in making a vile character someone filmgoers can root for.