The high concept: an avid reader of murder mysteries reads Macbeth, and tries to figure out who really killed King Duncan. Because Macbeth would be far too obvious an answer, of course.
Those two lines could be a neat throwaway joke by themselves. Except Thurber goes further than that. He actually manages to come up with a couple of alternate solutions for who killed Duncan. For example, “At first I suspected Banquo. And then of course, he was the second person killed. That was good right in there, that part. The person you suspect of the first murder should always be the second victim.”
Consider this logic: Lady Macbeth was clearly pretending to sleepwalk, because why would a sleepwalker be carrying a lit taper to see by? Therefore she must be trying to act guilty to shield Macbeth, even as Macbeth pretended to see a ghost in the banquet scene in order to deflect attention from Lady Macbeth; both think the other one killed Duncan, and are trying to protect each other. Meanwhile it’s Macduff who first discovers the body, and he’s the one who profits by all this by the end…
Hilariously clever, well worth finding. And the end is fantastic.
The Macbeth Murder Mystery by James Thurber
Availability: print only
Word count: 1,600
First published: 1942
Where to find it: My World – and Welcome to It, collection, 1987, Methuen
Thurber: Writings and Drawings, collection 1996, Library of America