A locked room

The pleasure of reading "fair play" mysteries isn't the murder itself, but how it was done. About "locked room" mysteries:

The rules of fair play mysteries are clear: the reader must be just as able to solve the crime as the central sleuth. All the clues must be on the page, the how and who must be logical and rational, and the final explanation can’t involve any supernatural sleight of hand.

But even fair play mystery writers like to play around. And sometimes that takes a particular, fun form: the locked room mystery. Part of a category known as impossible crimes or sometimes miracle problems, these mysteries usually feature a dead body, clearly murdered, in a room or space that has been sealed from the inside. There’s no apparent way that a murderer could have gotten in or out, perhaps even no obvious weapon—so how was the crime committed?

The fun of locked room mysteries, of course, is that they are part of the fair play genre: the reader knows the clues are there, that the crime was committed by a real person. The seemingly impossible nature of the crime adds an extra challenge to our armchair sleuthing. ....

Agatha Christie wrote many famous impossible crimes, including Murder in Mesopotamia (1936) and And Then There Were None (1939). ....

But no one can talk about the locked room genre without mentioning John Dickson Carr. Carr was American writer, but he lived in Britain for many years and is often grouped with British Golden Age mystery writers. He began publishing in 1933 and wrote dozens of crime novels, many of them locked-room mysteries like The Plague Court Murders (1934) or The Problem of the Green Capsule (1939). Carr is often considered the master of the impossible crime, and a panel of mystery reviewers and writers once selected his 1935 mystery The Hollow Man as the best locked-room mystery of all time. ....

Katharine Schellman, "Almost Two Centuries of Impossible Crimes: Locked Rooms in Detective Fiction," CrimeReads, August 23, 2022.