The Sleeping Sphinx, first published in 1947, is a detective story by John Dickson Carr

John Dickson Carr

John Dickson Carr was an American author of detective stories, who also published under the pen names Carter Dickson, Carr Dickson and Roger Fairbairn....

 which features Carr's series detective Gideon Fell

Gideon Fell

Doctor Gideon Fell is a fictional character created by John Dickson Carr. He is the protagonist of 23 novels from 1933 through 1967 as well as a few short stories. Carr was an American who lived most of his adult life in England; Dr. Fell is an Englishman who lives in the London suburbs.Dr...

. This novel

Novel

A novel is a book of long narrative in literary prose. The genre has historical roots both in the fields of the medieval and early modern romance and in the tradition of the novella. The latter supplied the present generic term in the late 18th century....

 is a mystery of the type known as a whodunnit.

Plot summary

Donald Holden, upon his release from the British Armed Forces, discovers that he has been announced as dead more than a year ago, which may complicate his love for the beautiful Celia Devereaux. When he announces the mistake to her, they are reconciled, but strange things have been happening to the Devereaux family. Celia's sister Margot died in mysterious circumstances more than a year ago, after an evening of spooky games during which each guest wore the death mask

Death mask

In Western cultures a death mask is a wax or plaster cast made of a person’s face following death. Death masks may be mementos of the dead, or be used for creation of portraits...

 of a famous murderer. The London offices of a fortune teller have been abandoned, but someone still uses them. And someone or something has been moving the coffins around inside a sealed mausoleum. Some people think that Celia has inherited the family taint of hysteria

Female hysteria

Female hysteria was a once-common medical diagnosis, made exclusively in women, which is today no longer recognized by modern medical authorities as a medical disorder. Its diagnosis and treatment were routine for many hundreds of years in Western Europe. Hysteria was widely discussed in the...

, but it takes the combined efforts of Donald Holden and Gideon Fell to explain Margot's death and the moving coffins.