The Twenty-Third Man is a 1957 mystery detective novel by the British writer Gladys Mitchell. It is the thirtieth in the long-running series of books featuring Mitchell's best known creation, the psychoanalyst and amateur detective Mrs Bradley.
Dame Beatrice Bradley is on holiday in the Canary Islands, staying on a smaller island famous for his cave where the bodies of twenty three mummified ancient kings are buried. However Karl Emden, one of the tourists, on the island appears as a twenty fourth corpse in the cave. Dame Beatrice begins to investigate the passengers who arrived with her, suspecting one of them is the killer.