The locked room mystery is an intriguing type of crime fiction that revolves around an offence being committed in such a way that it seems impossible to determine how it was done. Usually a murder victim is discovered in a room locked from inside with no other apparent exit or entry route, making the readers wonder how the killer gained access and then vanished into thin air!
The plot uses the ‘red herring’ technique in which the author deliberately casts an innocent person as guilty in order to distract or mislead the reader. The true culprit is armed with a seemingly unbreakable alibi and remains undetected till the end. The intelligent murder mystery is solved in a dramatic climax.
This format established itself as a sub-genre of crime fiction in the 19th century although some examples are also found in ancient Greek literature. The format gained popularity in the 1920s and 30s thanks to writers like Arthur Conan Doyle, Joseph Cummings and Agatha Christie.
John Dickson Carr is considered a master of locked room mysteries. His story ‘The Hollow Man’ (1925) was voted as the best locked room mystery ever by a panel of eminent mystery writers and reviewers in 1981.
Locked room mysteries are generally short stories as it is difficult to sustain a puzzle format in a novel.