In Acapulco, Hercule Poirot attends a dinner party in which one of the guests clutches his throat and suddenly dies. The causes seem to be natural until another party with most of the same guests produces another corpse.
When a priceless crown is stolen during a benefit gala held by the Lawrenceton library, Aurora and the Real Murders Club must investigate who would kill to get their hands on it.
A psychotic man opens fire in a diner, murdering numerous people before killing himself. The survivors struggle in different ways following this horrendous event: a doctor doubts his own instincts and elects to use an experimental medical procedure on his wife, while a gambler believes he's on a lucky streak. A waitress begins engaging in promiscuous sex, and a young girl whose father is among the dead gains unexpected fame.
Actress Jane Wilkinson wants a divorce, but her husband, Lord Edgware, refuses. She convinces Hercule Poirot to use his famed tact and logic to make her case. Lord Edgware turns up murdered, a well-placed knife wound at the base of his neck. It will take the precise Poirot to sort out the lies from the alibis - and find the criminal before another victim dies.
At the insistence of Ruth Van Rydock, an old schoolfriend who is convinced that there is something wrong, Miss Marple agrees to visit 'Stonygates', the country house of Ruth's sister.
After being double-crossed and left for dead, a mysterious man named Walker single-mindedly tries to retrieve the rather inconsequential sum of money that was stolen from him.