1938, London. The four queens of British crime fiction, Agatha Christie, Dorothy L. Sayers, Ngaio Marsh, and Margery Allingham, are hosting a gala to raise money for the Women's Voluntary Service to help Britain prepare for war. Baronet Sir Henry Heathcote has loaned Hursley House for the event and all the elites of London society are attending. The gala is a brilliant success, despite a few hiccups, but the next morning Sir Henry is found dead in the library. Detective Chief Inspectors Lilian Wyles and Richard Davidson from Scotland Yard are quickly summoned and discover a cluster of potential suspects among the guests, including an upset fiancee, a politically ambitious son, a reserved but protective brother, an irate son-in-law, a rebellious teenage daughter, and the deputy home secretary. Quietly recruiting the four queens of crime, DCI Wyles must sort through the messy aftermath of Sir Henry's death to solve the mystery and identify the killer.
