Time Out says
One of Resnais' most underrated explorations of the tone of time and memory. Claude Ridder (Rich), a failed suicide, is visited by two men who invite his cooperation in an experiment (already tried with a mouse) to project him into the past to see if he can recapture a moment of his life (since he has no wish to live, and therefore has no future, he is the perfect subject). Indifferently he agrees, is whisked through a suburban no man's land to a laboratory, and - accompanied by the mouse as an experienced travelling companion - sets off on his weird, fairytale trip through time, only to become hopelessly lost. As the scientists frantically try to trace their missing guinea-pig, fragments of his past surface momentarily, recurringly. Beautiful, tranquil, but increasingly menacing clues to a love affair with a girl he may or may not have killed. The fragments remain teasingly uncertain, just out of Ridder's grasp, but his feelings lead him inexorably back to the key moment of suicide; and in the present, Ridder's body - the body of a man projected into his death - is found in the laboratory grounds. On one level a witty sci-fi adventure, on another a poetic apprehension of man's helpless entrapment by time, the film is perfectly summed up by the extraordinary last shot of the mouse, still caged by the glass dome in which it has travelled, standing with its paws spread out against the glass in mute appeal.
Cast and crew