The investigator here is the agent of discord--a glib attorney, Mitchell Stephens (Ian Holm), who seeks out the citizens of a small Canadian town devastated by loss. On a slippery road, a school bus loaded with kids plunged into a frozen lake; in an instant, the townspeople were robbed of their children, their futures, and their illusions of security. Nothing will bring back the kids, Stephens pitches to couple after grief-stricken couple, but a huge class-action settlement will make somebody pay. Somebody must pay. But who?

The first rule of order is to assess the blame. "There's no such thing as an accident," the unflappable Stephens tells two "hippies" (Earl Pastko and Arsine Khanjian) whose will to live seems to have died with their adoptive son. But as the attorney pokes around the crash site, the suit triggers a rift among the town's grieving parents. For if the crash wasn't caused by negligence, it must have been cosmic retribution: for the hotel owner (Alberta Watson) who was cheating on her husband with the local mechanic (Bruce Greenwood); for the frustrated musician (Tom McCamus) who was forcing his dreams--and perhaps himself--on his pop-singer daughter (Sarah Polley).

The Sweet Hereafter is the most humane, and the most wrenching, of Atom Egoyan's prickly, dark-humored movies. On the surface, the film bears scant relation to Egoyan's ironic black comedies, whose clinical, poker-faced acceptance of aberrant behavior resembles a David Lynch quirkfest run through one of David Cronenberg's telepods. His most recent, the fascinating but coolly remote Exotica, started with a kinky situation--a bereaved father (again, Bruce Greenwood) obsessed with a schoolgirl stripper--and worked its way backward to show how we'd misjudged the motivations of everyone involved. But the director seemed more interested in tweaking the audience's voyeuristic expectations than in exploring the inner state of his characters.

In retrospect, the absurdist gamesmanship of those earlier movies was a warm-up for The Sweet Hereafter's daringly fractured style and its solemn, staggering depth of feeling. In its early scenes, The Sweet Hereafter moves effortlessly back and forth in time, contrasting the ravaged townspeople with their blissfully mundane lives before the crash. "Before the crash"--the phrase comes to haunt every frame. We feel for the bus driver (Gabrielle Rose) who chokes back tears in a room decorated with school pictures; somehow, though, it's even more upsetting to see the sweetly gawky woman exchanging banal pleasantries with smiling parents as they usher their kids onto the bus. The movie's splintered chronology ultimately removes everyone from the here and now--even Stephens, who agonizes over a junkie daughter whose life he once literally held in his hands. Grief erases the present tense; it leaves only a before and an after.

In various forms, in all of his movies, Egoyan has examined the impact of tragedy and the managing of loss. From the radiant first image, of a sleeping couple cradling a little girl, The Sweet Hereafter is suffused with a parent's anxious, consuming love for a child. (The use of Robert Browning's "The Pied Piper of Hamelin" as a suggestive refrain is inspired.) But Egoyan gives us a terrible gift he spares his characters: the knowledge of what is to come. We watch the town's placid routines of daily life--the father who follows the school bus every day and waves to his kids, the parents who insist on walking their boy to the bus stop--knowing that the good-luck rituals will fail. When we see the sleeping couple again, late in the film, we know what they'll awaken to. The characters can't even retreat safely into memory--there are too many guilty secrets, too much potential blame. When the lawsuit is resolved, in a courtroom scene all the more gripping for its lack of theatrics, it absolves no one.

The movie's icy calm is enhanced by Paul Sarossy's cinematography, which emphasizes the town's isolation and the heavy expanses of snow, and by Mychael Danna's serene madrigal strains on the soundtrack. As Stephens, Ian Holm lends ambiguity and humanity to what could've been a stock shyster role, and the supporting cast is wondrous, from Sarah Polley's quietly accusing survivor to Bruce Greenwood's anguished father. And there are countless moments of piercing beauty, culminating in a guilt-stricken look of remembrance exchanged on a crowded street, years after the crash, between two survivors who want nothing more than to forget. The Sweet Hereafter offers no comfort, only the experience of its sorrowful truths, and the emergence of a once promising filmmaker as a great one.