The Red Signal is a short story, written by Agatha Christie.
A dinner party is taking place in the London home of Jack and Claire Trent. Their three guests are a Mrs Violet Eversleigh, Sir Alington West (a noted psychiatrist), and West's nephew, Dermot West. The talk turns round to precognitive abilities and premonitions which Sir Alington is dismissive of, believing them to be both coincidences and situations that are talked up after the event. Dermot is not so sure and describes such feelings as having a red signal – "danger ahead!" – and tells one story of near-death in Mesopotamia when he avoided being murdered by an Arab servant. What he does not tell the group is that he is experiencing the red signal tonight at the dinner party. He ponders who could be the source of danger, his thoughts moving to his love for Claire Trent, a feeling that he constantly suppresses in view of the fact that Jack Trent is his best friend. Coming out of his reverie, the conversation has turned to madness and the dangers of suppressing delusions. Sir Alington looks pointedly at Claire Trent who is visibly disturbed by this talk.
One of the purposes of the evening is to meet a medium who is there to conduct a sitting. She does so and warns one of the people in the room not to go home as there is danger there. The party breaks up and Sir Alington asks Dermot to accompany him home to Harley Street before going on to join his friends at the Grafton Galleries. Once inside, he tells his nephew that he knows of his infatuation for Claire and not to give into it. He disapproves of divorce and speaks of a history of insanity in their family and his suspicions of homicidal mania. The discussion becomes emotional and Dermot utters a threat to his uncle, one which is overheard by the manservant, Johnson, as he brings in drinks. Going to the Grafton Galleries, Claire tells Dermot that his feelings for her are shared and because of this she wants him to go away. He asks her to join him but she refuses.
Going back to his flat, Dermot is once again assailed by the feeling of danger and, to his astonishment, finds a revolver hidden in a bedroom drawer. There is a knock on the door and Dermot opens it to the police. The feeling of danger makes him tell the police that he is Milson, his own manservant, and the police tell him that his "master" is wanted for the murder of Sir Alington who was shot dead earlier that night after being overheard arguing with his nephew. The police search the flat, find the revolver and decide to leave an officer there in case West "comes back". Dermot escapes from the flat through the kitchen window while supposedly getting drinks and quickly bumps into Jack Trent who gets him away to his own house. He locks himself in a room with Dermot, produces a gun and then insanely confesses to the murder. Sir Alington recognised his condition and was at the dinner party to assess his true mental state. Dermot assumed that his uncle was speaking of Claire who was actually assisting Sir Alington in his diagnosis. She now also assists the police gaining entry to the house and the locked room. Jack shoots himself before they can take him.
- The first UK magazine publication: The Red Signal: First published in issue 232 of The Grand Magazine in June 1924.