The narrator befriends a railroad signalman at his lonely post outside a tunnel. The signalman confides that he is being haunted by a ghost. The apparition warned him on two previous occasions of impending tragedies; a horrible accident and a sudden death of a passenger. The specter has recently reappeared and the signalman is tormented by the thought that something terrible is about to happen. The narrator is concerned but skeptical. Soon, however, he learns the meaning of the third ghostly warning.