The Coen Brothers’ follow-up to their triumphant “O Brother, Where Art Thou?” might be characterized as an existentialist take on the classic film noir of the 1940s. As perfectly crafted as all their films, and shot in a black-and-white that imparts a luminous glow to the images, “The Man Who Wasn’t There” is, in many respects, a mirror-image of the earlier picture (indeed, the very title may be intended as a wry response to the question posed by that of the “O Brother”): it’s deliberate where “Brother” was antic and pensive instead of rambunctious; it’s set in an era of growing prosperity and promise rather than one of economic depression; and its central character is as solemn and quiet as Everett Ulysses McGill was voluble and energetic. (They both are obsessed, though, with hair–though in very different ways.) Most importantly, while “Brother” was ultimately about trust and family, “Man” is about infidelity and isolation–though it treats of those subjects from a darkly humorous stance.

The story is set in Santa Rosa, California (an obvious reference to Hitchcock’s “Shadow of a Doubt”) in 1949. The protagonist is Ed Crane (Billy Bob Thornton, looking remarkably like Raymond Massey), a gaunt, almost preternaturally still barber who stoically endures the dalliance of his wife Doris (Frances McDormand) with her boss Big Dave (James Gandolfini), the manager of a local department store, appropriately called Nirdlinger’s. Ed works for Doris’ brother Frank (Michael Badalucco)–he inherited the shop from his father–who’s as talkative as Ed is impassive. Ed’s world is changed when he meets a sweaty, toupee-wearing hustler named Tolliver (Jon Polito, looking ridiculously like Akim Tamiroff in Orson Welles’ “Touch of Evil”) who’s seeking financing for his revolutionary dry-cleaning business. He decides to get funds to invest With Tolliver by blackmailing Big Dave. The scheme backfires, however; he secures the money, but Dave gets wise. Before long Doris is jailed, and Ed and Frank have to scramble to hire a top-notch defense attorney named Riedenschneider (Tony Shalhoub) for her. As a sideline, Ed grows intensely interested in Birdy (Scarlett Johansson), the daughter of lawyer Walter Abundas (Richard Jenkins), whose amateur piano-playing he so admires that he wants to turn her into a professional. The youngster obviously represents a sort of muse calling Ed to something beyond his present existence, and over the course of the film he does reach a new level–though the convolutions of the plot make it a different one than he had hoped.

But the circuitous route that “The Man Who Wasn’t There” takes, while intriguing, isn’t nearly as important in the last analysis as the remarkable technique with which the brothers Coen conduct the journey. Every frame of the picture is thought out with a care that most filmmakers don’t exhibit through an entire feature (special note should be made of Polito’s final scene, which ironically recalls an extraordinary moment from Charles Laughton’s “The Night of the Hunter”), and quirks and oddities punctuate the narrative to startling effect, even though as a whole the film radiates a calmness that’s almost overwhelming. At the center of it all is Thornton, whose minimalist turn as Ed is a triumph that proves that less is often more; together with his flashier performance in “Bandits,” it insures that 2001 will be a memorable year in his career. The rest of the cast is solid across the board–certainly Gandolfini goes far to compensate for his misbegotten performance in “The Last Castle”–but all play second-fiddle to him. That’s particularly true of McDormand, who’s really given very little to do–rather surprising given that she’s writer-director Joel’s wife. The only serious disappointment is Shalhoub; he gamely tries to embody the lawyer’s extravagant self-absorption, but seems too small for the part’s oversized dimensions. Even still, Riedenschneider’s musings about the Heisenberg uncertainty principle get the chuckles they deserve.

The music to “The Man Who Wasn’t There” includes an original score by Carter Burwell and a few popular pieces from the period, but it’s mostly drawn from classical compositions, especially piano pieces by Beethoven. In Beethovenian terms, one could say that the picture is slighter than some of the Coens’ other work, less a full sonata perhaps than a bagatelle–one of the more languorous, gentler ones, of course. But a bagatelle this beautifully realized deserves to be heard, or, in this case, seen. Its jeweled brilliance and exquisite craftsmanship are treasurable. “The Man Who Wasn’t There” is a lovely, very funny and strangely moving film, one that takes its rightful place in the ever-more-amazing corpus of the brothers’ work.