The Case of the Constant Suicides, first published in 1941, is a detective story by John Dickson Carr. Like much of Dickson Carr's work, this novel is a locked room mystery, in addition to being a whodunnit.
Members of a large and widespread Scottish family are brought together at a highland castle in order to resolve various pieces of family business following a death. Suspicious events soon begin to occur, the body count rises, and a verdict of suicide is not necessarily to be trusted. Enter the gargantuan Doctor Gideon Fell, who applies his substantial powers of deduction to the problem of how men can be indirectly murdered while they're inside locked, sealed and inaccessible rooms.