When James Wilson retires from journalism, he decides to settle down in a small Welsh town with a roomate, a Mr. Cedric Coombes, and at first thinks little of his new friend's eccentric behavior. But he can't shake the feeling that he knows him from somewhere else. As Coombes displays his astonishing deductive prowess, and becomes embroiled in the police investigation of the bizarre death, and apparent murder, of a man in a bathtub, Wilson, or should we say Watson, begins to wonder just who this Coombes really is.