While in his office, Superintendent Sinclair receives a phone call from an unknown caller, who claims that they murdered the Home Secretary in his home. Together with Sylvester Collins, an eccentric sleuth, Sinclair goes to the Home Secretary’s house to investigate the truth of the call, only to discover the body of the victim in a locked room. Is this a bizarre suicide, or is it a skillfully executed murder? This is the question the duo have in mind as their investigation digs deeper into the victim’s relationship with his daughter and estranged son.

Written in 1926, the peak of the Golden Age of Detective Fiction, Walter S. Masterman’s The Wrong Letter follows a typical whodunit structure centered around a locked-room mystery, yet the novel stands out with its intricate clue-puzzle and its fresh take on the classical detective-and-assistant dynamic. While Collins and Sinclair’s relationship initially resembles Sherlock Holmes and Watson’s, it soon evolves beyond a mere archetype.