(The Woman in Black)
Trent's Last Case is actually the first novel in which gentleman sleuth Philip Trent appears. The novel is a whodunit with a place in detective fiction history because it is the first major sendup of that genre: Not only does Trent fall in love with one of the primary suspects — usually considered a no-no — he also, after painstakingly collecting all the evidence, draws all the wrong conclusions.
Convinced that he has tracked down the murderer of a business tycoon who was shot in his mansion, he is told by the real perpetrator over dinner what mistakes in logical deduction he has made in trying to solve the case. On hearing what really happened, Trent vows that he will never again attempt to dabble in crime detection.