InsomniaDirected by Christopher Nolan A Warner Bros. release Opens Friday at area theaters

The sun doesn’t go down in Insomnia. It shines relentlessly, bleeding through drawn blinds and door cracks, at all hours. All this light makes it hard for Detective Will Dormer (Al Pacino) to get any sleep. On loan from the L.A.P.D. to the decidedly smaller department in Nightmute, Alaska, Dormer arrives with his partner, Hap (Martin Donovan), via a rocky biplane ride. Looking out over the bright white snowy mountains as they approach, Hap worries that there’s nothing out there. In response, Dormer looks exhausted. And this is before their investigation has even begun.

The significantly named Dormer's inability to sleep is thematic, of course, much as Leonard Shelby's lack of short-term memory was in Nolan's Memento. Dormer's called in to solve a horrific murder, the brutal beating death of a high school girl, at the hands of someone who then washed her hair and clipped her nails before he left her body at the local garbage dump. Following the requisite morgue scene -- where body parts, wounds, and a few hard-to-read flashbacks to the crime appear in close-up, gorgeously shot by Wally Pfister -- Dormer opines, "this guy stepped over the line and he didn't even blink."

As this showy pronouncement suggests, Dormer knows something about stepping over lines. He comes equipped with a complicated, evidently shady history, rendered in deft, if somewhat obvious strokes. Hap carries an L.A. newspaper with a headline concerning corruption in the homicide division, and he and Dormer have a neatly explanatory argument about Hap's decision to submit to pressures from Internal Affairs, clearly set on "getting" Dormer. This argument leads to tension on the job, as they investigate the murder, and eventually, to what appears to be a terrible accident, Dormer's fatal shooting of his partner while they're chasing the shadowy suspect across a foggy, rocky terrain. Will says the now-disappeared suspect shot Hap, and since no one saw anything, it looks like he'll get away with it.

With this background, Nolan's film provides a denser, deeper characterization of Dormer than its source, the exquisitely spare and haunting 1997 Norwegian film by Erik Skjoldbj¾rg, also called Insomnia, wherein Stellan Skarsgård's detective's motives must be culled from his actions. Afraid and not a little creepy, he doesn't do nearly the amount of talking and emoting that Pacino does. He's actually subdued here, compared to some of his other recent performances, say, in Any Given Sunday and The Devil's Advocate. Sans hoo-ah, he gives a perversely compelling performance.

This lower-key approach seems to have rubbed off on co-star Robin Williams, who might easily have given Pacino a run for his scenery-chewing money. He plays the murderer, Finch, a cheesy crime novelist who professes "admiration" for Dormer's profession, then names himself Dormer's new "partner," since he knows what happened with Hap. Their relationship evolves speedily, as Finch insists on calling Dormer in the middle of the luminous night, nattering on about guilt and accidents (he claims the murder was also inadvertent, though, as Dormer points out, it took him 10 minutes to beat the girl to death).

Dormer's self-doubts take him for a wild ride inside his own mind, along with Hap's ghost and a few harder-to-parse memory fragments. And so he's drawn, apparently inexorably, into Finch's moral murkiness, a point made too obviously ironic because of all the damn light. Their relationship is all about looking and being afraid to look, bobbing and weaving: one dramatic set piece has Dormer chasing after Finch across a river of logs -- as Finch scampers from rolling surface to rolling surface, Dormer takes a tumble, made more alarming by the fact that the logs move with the current, slamming into one another and blocking Will's desperate efforts to break through to the surface.

Inasmuch as Finch is vaguely right (they are "alike," having killed and lied about it because they were able), the two descend into a fairly standard movie-cop-killer relationship, with each trying to out-posture and out-think the other, with Dormer's part rather severely hampered by five or six nights without sleep. Given that Finch's favorite means of connection is the phone -- he even calls Dormer at Finch's own home, knowing he's there snooping about, invites him to take a shower and asks him to feed his dogs -- the relationship becomes intensely intimate, even vaguely erotic. These guys can't get enough of each other or themselves.

Into the midst of this boy-boy action steps Ellie Burr (Hilary Swank), the eager young detective assigned to help get Dormer around town (as she gushes on their first meeting, she studied his cases in school). Even when she suspects something's not quite right, she goes along, hoping her idol will pull it out and not be the fallible, if well-intentioned vigilante he seems to be. Her will to waking, which affects Dormer's choices by the end, makes Nolan's film less dire than Skjoldbj¾rg's, but also less elegant.