Hastings renews his friendship with Poirot and involves him in the mysterious poisoning of the mistress of a manor house married to a man twenty years her junior.
At a flower show, an older woman in a wheelchair approaches Poirot, gives him an empty seed packet, and asks him to visit her the next day. When Poirot arrives the next day, the woman is dead, murdered with poison.
Poirot is entrusted with transferring $1 million in Liberty Bonds to America on the Queen Mary, but the bonds are cleverly stolen anyway.
A mining entrepreneur hires Poirot to solve the brutal murder of his daughter and the theft of her jewels aboard the express train to Plymouth
Poirot realizes that a murder is being plotted, and with the help of Hastings' latest hobby, he sets out to prevent it.
Poirot is drawn into a case where a man is found dead on the grounds of his estate, apparently frightened to death by the spirits that haunt it.
Poirot helps Chief Inspector Japp try to find a jewel thief, but is sidetracked when a bewitching Russian countess arrives on the scene.
Poirot is asked to protect a woman from her violent husband, but events take a turn when the husband soon becomes the victim of a gruesome murder.
Poirot reluctantly agrees to help an Egyptian prince recover a valuable royal ruby that was brazenly stolen from him during the Christmas holidays.
Poirot and Hastings attend the Victory Ball, a popular costume party. During the festivities, one of the guests is found stabbed to death, and another succumbs to a drug overdose the next day.
Poirot is taken ill during a weekend shooting party, which ends when the unpopular host is found murdered in his study.