Pretend for a minute that Christopher Nolan's extraordinary Memento is nothing more than a gimmicky noir exercise, grinding out its plot with cool efficiency and hollow mechanics, devoid of any larger significance. Disregard its mind-bending profundities about the nature of memory and existence and what it means to be human. Even if all these things were willfully ignored and Memento were simply reduced to an architectural blueprint, it would still be akin to watching Bobby Fischer play chess, seeing the board several moves ahead of his opponent. It's an exhausting experience just to keep up—be sure to arrive on time and stay seated until the credits roll—but for Nolan to dream up a scenario this complex and yet work it out so thoroughly seems almost inconceivable. His story marries two high concepts that would be baffling enough on their own, let alone together. Traumatized by his wife's rape and murder, Guy Pearce suffers from a rare neurological disorder called anteriograde amnesia that prevents him from creating any new memories. Basically, the world as he understood it 10 minutes ago has evaporated from his mind without a trace. In order to exact revenge on his wife's killer, Pearce has devised an elaborate system of tattoos, Polaroids, note cards, and file folders to help him piece together the facts. He also has to uncover the possible ulterior motives of shady ally Joe Pantoliano and a sullen bartender played by Carrie-Anne Moss. To further complicate matters, Nolan begins with the end and ends with the beginning, so the action takes place in overlapping fragments that move backwards in time. On top of all that, he inserts black-and-white scenes of Pearce on the phone in his motel room, telling the harrowing story of a fellow amnesia sufferer (Stephen Tobolowsky) he met in his days as an insurance claims investigator. Memento has endless fun playing with hiccuping time and ephemeral memory: In one of its funniest scenes, Pearce wonders if he's being chased or giving chase; in one of its most suspenseful, he scrambles to find a pen before he forgets a person's diabolical abuses. For a while, Nolan's twin gimmicks seem to exist solely for clever gamesmanship, like the achronology in his low-budget neo-noir debut, Following. But the astonishing payoff takes the film to another level entirely, unleashing a battery of existential questions that shed new light on everything that precedes it. More than just a shallow mindfuck, the twist in Memento is that there's more going on than the head can hold.