"Memento" opens with a seemingly motionless shot of a disturbing Polaroid photograph. A dead body lies face down with a bullet wound in the back of the head. As this shot lingers, the image in the snapshot begins to fade and lighten. Suddenly, the hand holding the photo shakes it around a little, like one does when waiting for a Polaroid to develop -- and the picture fades further. Soon the image of the body is gone completely.

By the time the blank photo jumps back into the camera and the flash goes off, you've already realized you're watching events unfold in reverse. Blood seeps up a wall and a gun flies back into the hands of the man with the camera. Bullet casings leap off the floor and reunite with bullets re-entering the barrel. The dead man stands up. You've just witnessed a murder -- backwards.

While the rest of action takes place in forward gear, the story of "Memento" continues to be told in retrograde. Writer-director Christopher Nolan ("Following") takes us back in time a few minutes to learn that the dead man, Teddy (Joe Pantoliano), was killed by Leonard Shelby (Guy Pearce) as vengeance for the rape and murder of his wife. More importantly, we learn that Leonard received a blow to the head while trying to save her and it severely damaged his short-term memory.

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