Was It Murder? deals with the phenomenon of coincidence by posing the question of how likely it is that two brothers attending the same boarding school meet with two separate accidental deaths - and curious ones at that - within the same school year. In the manner typical of the Golden Age whodunnit, the solution is only presented in the final pages of the novel. Throughout the book, an amateur sleuth and a Scotland Yard detective vie with each other to solve the riddle, with only one of them successful in the end.
