The Lemesurier Inheritance

Hercule Poirot and Hastings meet Captain Vincent Lemesurier and his uncle Hugo, a chemist. Cousin Roger tells them about a curse that has plagued the family since the Middle Ages, in which no firstborn son has lived to inherit the family estate. Poirot and Hastings learn the next day that Vincent has committed suicide by jumping from his train during the journey home. Over the next few years, all other potential heirs die under various circumstances, leaving Hugo to inherit the estate.

Poirot receives a visit from Hugo's young wife, an American who does not believe in the curse. She worries about her eight-year-old son, Ronald, who has had three narrow escapes from death in the past few months. Poirot and Hastings travel to the home in Northumberland and renew their acquaintance with Hugo, who believes that Ronald is doomed and that the couple's younger son Gerald will inherit. Poirot takes note of one of Ronald's mishaps, in which he fell while climbing down an ivy vine that had been deliberately severed.

A report comes in of Ronald being stung by a bee, drawing Poirot's concern. He and Hastings keep vigil in Ronald's room that night; when a figure creeps in and tries to poison Ronald with an injection, the two men overpower him and discover him to be Hugo. He had engineered the deaths of the other family members in order to inherit the estate and, having gone mad, was trying to maintain the legend of the curse by killing Ronald; the "sting" was actually a sedative. He is placed in an asylum, and Ronald inherits the estate upon his death. However, Poirot muses that Ronald may not be Hugo's biological son, noting that his hair colour matches that of Hugo's secretary, and that the curse may yet live on.