"Untraceable" is a movie that attempts to get at something important: What is the proliferation of Internet atrocity footage -- the easily clickable mix of shootings, beheadings and other mortal calamities -- doing to us? What has it already done? In addressing this subject, director Gregory Hoblit has to walk a fine line between conveying its essence realistically and turning his picture into torture porn itself. Hoblit succeeds more than many might, I suppose. But by the end of the film, when the resident madman cranks up his shredder and another victim begins to squeal, you might as well be watching "Saw V."

The setting is damp, leafy Portland, Oregon, where local FBI cyber-crime investigators have discovered an alarming new Web site. It's called "Kill With Me," and it offers viewers the thrill of live, streaming murders with an appalling bonus kink -- the higher the viewer numbers rise, the quicker the victim dies. "Don't call them fans," one agent says of the millions of snuff junkies tuning in. "They're accomplices." The movie, of course, turns us into accomplices, too, which is the not-entirely-novel point.

The KWM webmaster is a computer savant of fiendish expertise. He continually changes his IP address ("He's got to be running his own botnet," says one tracker), and he closes the site down immediately after each killing. He's untraceable and, for the moment, unstoppable. But FBI agent Jennifer Marsh (Diane Lane) is determined to nail this freak, and she's assisted in her mission by fellow cyber agent Griffin Dowd (Colin Hanks) and a Portland homicide detective with the odd name of Eric Box (Billy Burke).

As these three pursue investigative dead ends, the madman they're chasing continues his depredations, trolling for victims, subduing them with Taser shocks and lugging them down to his basement dungeon for final rites. His methods are horrifically inventive: We see one lacerated victim hooked up to an IV filled with anti-coagulant, so that his unclotting blood slowly drains away; and we watch another doomed soul being roasted to death by a battery of sun lamps. It must be admitted that these atrocities aren't presented with the relish typical of standard-issue gore flicks -- the garish video images in which we see them played out have a distancing effect. After the first couple of slaughters, though, the boundary between illustration and exploitation begins to blur. And by the time we see Agent Marsh herself bound up and dangling from a pulley, it's disappeared altogether.

The movie has some good things going for it. The always excellent Lane may have an insufficiently complex character in which to invest her abundant talent (despite the endangered daughter with which she's been accessorized); but Billy Burke (of "Fracture"), as the sympathetic cop who takes a personal interest in Marsh's safety, has a gentle, melancholy charm that's unusually appealing. And 21-year-old Joseph Cross ("Flags of Our Fathers") is chillingly weird in his early scenes as the online maniac (who has his reasons, as it turns out).

But the picture is grimly unpleasant, and the formulaic conclusion subverts whatever earnest intentions were present at the beginning. The movie does leave us mulling one bleak thought, though. It's expressed by a character who says, "Soon, executions will be delivered live to our computers, our phones, our hand-helds. They'll have no trouble finding sponsors." If nothing else, "Untraceable" is a reminder of how near that day may be drawing.

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