When five bruised, bloodied or bound men each awaken in a locked building at some seemingly abandoned industrial site, it's understandable that one might see Saw. Unlike that horror-movie franchise whose films begin in similar fashion, however, this feature debut by screenwriter Matthew Waynee and director Simon Brand is a knife-sharp psychological action thriller that beyond its macho mechanisms is all about the malleability of identity, and alliance based on gut trust of perceived character and the logistics of immediate expediency.

An unidentified man (Jim Caviezel) in a blue-jean jacket comes to on the floor of some concrete warehouse outside of, he later learns, Nogales, Arizona. Around him is the aftermath of some clearly criminal undertaking: an apparent corpse (Greg Kinnear) near a bloodied shovel, an older bald man (Joe Pantoliano) tied to a chair, a badly wounded bearded guy (Jeremy Sisto) hanging by a handcuff from a railing, and a broken chair with bindings around it, suggesting someone was there and got loose. Blue Jean (as the end credits call him) doesn't even remember who he is, let alone what happened; no one seems to have any ID, suggesting outside involvement. That, at least, gets confirmed when a telephone rings, and Blue Jean, giving clipped, vague responses, learns a couple of names and that the caller's arriving in a couple of hours. Parallel scenes recount a kidnapping investigation involving a wife (Bridget Moynahan) and various law-enforcement guys (including David Selby, Chris Mulkey, Wilmer Calderon and DiCaprio clone Clayne Crawford) who, while decent and professional, aren't "CSI" super-cops.

As Blue Jean tests various dead-end escape routes, the others wake up. These include the unbound guy, credited as Rancher Shirt (Barry Pepper), and the not-dead Broken Nose (Kinnear), who finds a discarded newspaper revealing that two real-estate developers have been kidnapped. Their names, Coles and McCain, match what Blue Jean heard on the phone. So which of them are Coles and McCain, which are the kidnappers, and which of them is possibly someone else?

It's an intriguing set of circumstances--that nice, decent guy over there with whom you're developing a rapport could have been trying to kill you, or maybe was already your friend-that in lesser hands could all just play out as a clever chess game and nothing more. But the talented makers of Unknown get beyond the plot schematics of trust, calculating lies and possibly recovered memories to reach something sublime: the idea of the human being as a social animal who, given the chance to step outside the existential exigencies of life, believes that he's intrinsically decent. But is he really?

That's the question as--a couple of them doing it grudgingly, a couple not--the men eventually work together to deal with whatever's going to come through that door. They drop the very real need for self-identity and, to various extents, undergo reinventions that all culminate in one of those scenes I'm a sucker for, where somebody starts whistling or singing, and one by one others recognize it and join in, desperate for some connection out of the unknown.

Then, of course, it gets all Reservoir Dogs. And look what happened to that first-time filmmaker.