In The Skull and Crossbones Murder Case, Mr. Keen is called to investigate the shocking murder of Lemuel Barker, who is poisoned during a quiet dinner with his young wife, Audrey. The scene is set in their elegant New York mansion, where an air of unease permeates the atmosphere. As the couple finishes their meal, Lemuel suddenly collapses after drinking his coffee, and Audrey is left horrified to discover that her husband is dead. The police quickly determine that he was poisoned, and suspicion falls on their housekeeper, Emily Cross, who mysteriously disappears before they can question her.