We have a new champion screen chameleon on our hands. Stars have put on weight for roles before, and others have bulked up or slimmed down, but no one has gone as far as Christian Bale. To play Trevor Reznik, the title character of Brad Anderson’s “The Machinist,” Bale lost more than sixty pounds; the old phrase “skin and bones” applies to him quite literally–he actually looks like a concentration camp survivor.

But there’s more to Bale’s performance than weight loss. His physical appearance is certainly striking, but it would seem little more than a stunt if the actor didn’t match it with a characterization that’s equally so. Keeping almost unnaturally calm, moving and speaking with a deliberation that accentuates the strangeness, Bale creates a haunting figure of a man actually decomposing before our eyes–mentally as well as bodily. It’s a remarkable tour de force.

As far as his vehicle is concerned, “The Machinist” is one of those intricate paranoia pieces that teases you with dark hints and ghoulish imagery before tying up the disconnected strands into an explanation you’ll find either vaguely satisfying or positively frustrating. (Compare, in their very different ways, “The Usual Suspects” and “Memento.”) Bale’s character, whom we first glimpse wrapping a corpse in a rug and trying to dispose of it in a river (a scene that calls to mind the swamp sequence from “Psycho”), turns out to be a razor-thin, oddly standoffish machine operator at some sort of equipment factory, where his boss gives him a hard time and his co-workers look at him askance. Off the factory floor, he lives a simple, rather dreary life, keeping a dismal apartment, periodically checking the further decreases in his weight and constantly–obsessively–scrubbing the kitchen floor (and washing his hands) in bleach. His only outside pastimes, it appears, are going to an airport diner where he talks to a good-natured waitress named Marie (Aitana Sanchez-Gijon) and visiting his neighborhood prostitute Stevie (Jennifer Jason Leigh), who treats him with a pleasant familiarity. Reznik’s life takes an even bleaker turn when, distracted by a new hire at the factory–a strange, lumbering brute named Ivan (John Sharian)–he’s responsible for an accident in which Miller (Michael Ironside), a guy he’s helping with an electric drill, loses an arm. Now pretty much a pariah with his bosses and his co-workers, Reznik increasingly descends into even more of a waking nightmare. Everyone else says that Ivan doesn’t exist, but Trevor regularly runs into him, to his dismay, and comes to believe that somebody is out to get him–a paranoid reaction that ultimately destroys his relationship with Stevie. On the other hand, he grows closer to Marie, even going off on a Mother’s Day outing with her and her young son, an afternoon that’s very pleasant until he and the boy visit a very unusual haunted-house ride that culminates in the youngster suffering a seizure. From this point Trevor’s disintegration–both physical and mental–accelerates rapidly, until the reason behind his distress is revealed.

This is the sort of “Twilight Zone” story that toys with the viewer by forcing him to perceive things from the perspective of a character who might in fact be going mad, and whose experiences are fragmentary and puzzling under any circumstances. If not carefully handled that can lead to narrative chaos, but writer Scott Kosar and director Brad Anderson manage to keep things clear–if challengingly obscure–and, in tandem with designer Alain Bainee and cinematographer Xavi Gimenez, who bathe the images in grim greens and greys, they maintain a properly menacing mood through the very end. All the cast members contribute strongly to the atmosphere of drabness and malaise–Leigh, Sanchez-Gijon and Ironside are especially notable, and though Sharian comes across as a rather blunt instrument, he too has his moments. But it’s Bale who dominates. He’s in virtually every scene, and never flinches or falters. You won’t easily dismiss the sight of his emaciated frame from your memory, and his performance certainly whets the appetite to see how he’ll look–and act–as the young Bruce Wayne. There’s also a strong score from Rogue Banos, which accentuates the ties to “Psycho” by sounding more than a little Herrmannesque–though, it must be said, rather more like that composer’s later work for De Palma than his subtler efforts for Hitchcock.

The forbidding feel of “The Machinist” may well alienate many viewers–as also will the unsettling appearance of its troubled protagonist. And the denouement may well come as a disappointment after the complexities that lead up to it. But while it’s hardly a great movie, thanks to Bale’s remarkable performance it’s a genuinely creepy and engrossing one. What’s ultimately revealed to be Trevor Reznik’s guilt trip is something more than just a guilty pleasure for the audience.