A 20th-century Londoner named Euston is on a train when a white-faced stranger gets on who appears ill. The stranger sees the book the Londoner is reading about dreams, and starts to tell him about a series of bizarrely realistic dreams that he had which took over his life. These dreams take place hundreds of years in the future in Capri, and the stranger is a man of power and influence who has chosen to give up his power so that he can live with a younger woman that he loves. Many people implore the stranger to return to his position when a corrupt man rises to power and threatens the possibility of war. The stranger refuses to go back to his old life, so he is forced to experience the fall of Capri and the beginning of a World War over several weeks in these dreams. The stranger has never been to Capri in real life, but he is able to describe it in detail as well as other aspects of the dreams. He also describes war planes, although they do not yet exist. Ultimately, the stranger watches the woman he loves get killed in the war, and he experiences his own death shortly after. As the stranger finishes recalling his dreams, Euston realizes that the train they are on is becoming more clamorous and the atmosphere outside is foggy, and people are calling his name. The stranger reveals that he kept on dreaming even after he was killed and birds were tearing apart his body.