Paul Devereux is a fearless adventurer who rarely speaks about his past. One evening, however, he tells a friend about a strange dream he had many years before. In it, he watches a night train rushing through the darkness and sees a mysterious man enter a carriage where two people are sleeping. Devereux can see everything, but he is unable to move or warn them. For a time, he forgets the disturbing dream. Then, three years later, he is traveling through France with his young wife, Lucille, when events begin to look frighteningly familiar...