In the short story The Red Signal, Dermot West is the nephew of Sir Alington West. He is in love with Claire Trent, the wife of his best friend. During the course of the story, Dermot attended a dinner party at the London home of Jack and Claire Trent. Sir Alington and some others are also among the guests. After dinner, a seance is conducted where the the medium gets a message that one of the gentlemen present should not go home because there will be danger and blood.
After the seance, Sir Arlington asks Dermot to go back with him. At Sir Alington's residence, he tells Dermot that "Claire is not for you" and the whole idea of divorce to marry Dermot is out of the question. Dermot disagrees with his uncle and there is a violent argument which is overhead by Johnson, Sir Alington's manservant. Dermot leaves to join his friends at a nightclub.
When Sir Alington is found murdered that night, the Johnson's account of the argument and the fact that Dermot is Sir Alington's heir makes him the prime murder suspect.