Let's give points for ingenuity. "Memento" has a most ingenious structure: It tells its story from end to (almost) beginning, by staging each scene normally but then cutting to the scene which preceded it in time. After an opening closeup under the credits in which we see a Polaroid photo moving backwards from full development to undeveloped blank, the film's action takes us back through a man's search for the person who raped and killed his wife.

The problem for Leonard Shelby (Guy Pearce), a former insurance investigator - shades of a dozen 1940s noir films - is that he was hit on the head during the assault and has lost his short-term memory. He can remember everything in his life up to the murder, but now fights desperately to hold onto anything at all for more than a few minutes. He remembers no one he's met, nothing he's done, nor even where he lives, and relies on Polaroid photos he takes and makes notes on: 'She will help you.' 'Don't trust his lies.' And he has tattooed his body with more hints. Names, license plates, admonitions.

Each scene - just a few minutes of screen time - ends and a previous one appears. Slowly we gather more information, even though we're moving backward in time, against logic, rather than forward. But what is that information? Can it be trusted? Who is friend and who is foe? Neither we nor Leonard can be sure.

And here is where the film lets us down. Since we move from present to past, and in the present Leonard knows more than he knew previously, the film locks itself into a conundrum that can't be unraveled. That doesn't mean there isn't a revelation of sorts, or possibly more than one, but it does mean that there is no catharsis, no settling of scores, no resolution to a film whose thesis is that there must be an answer. It relies on a gimmick, in other words, that by definition precludes any real solution.

Moreover, Pearce is an odd and to me unsuccessful choice for the lead. Without affect, playing in a monotonous voice that's little more than a bark, and without any kind of grace to his movements, he is uninteresting to look at and boring to hear. He is not helped by a script that's more indicated than written, with scene after scene consisting of little more than plot points.

Writer-director Christopher Nolan, working from a rough outline for a story created by his younger brother, has inserted a running, parallel tale of a middle-aged couple whose husband has also lost his short-term memory - a couple Shelby had earlier encountered in his work as an insurance investigator. The question for that couple was whether or not the husband was simply pretending to have lost his memory; and the story's tragic resolution is obviously supposed to lend weight to Shelby's situation. But the stories do not parallel each other, and there is no lesson from the one that carries over into the other; it serves as little more than a time-filler.