An outbreak of apparent kleptomania at a student hostel is not normally the sort of crime that arouses Hercule Poirot's interest, but it is a bizarre list of stolen and vandalised items: a stethoscope, some lightbulbs, some old flannel trousers, a box of chocolates, a slashed rucksack, some boracic powder and a diamond ring later found in a bowl of a soup. Celia Austin quickly confesses to the pettier incidents to attract the attention of a male student....

In a suicide's room, seven clocks tick ominously, and the last words of a dying friend are "seven dials." The enigmatic sevens lead Jimmy Thesiger and his dashing cohort "Bundle" Brent to a Soho club. There they learn of the Seven Dials Society: seven masked conspirators who meet in a secret room to talk about stealing scientific secrets and hushing up murder.

Jack Argyle has died in prison, wrongly accused of the murder of his adoptive mother Rachel, and now everyone in the Argyle family looks suspicious.

When one of Sir Charles Cartwright's houseguests is poisoned, the master sleuth Hercule Poirot focuses his attention on the group of aristocrats and theater personalities gathered there for the weekend festivities.