A half-demented blackmailer named Sigurd Repellen confronts Jenny Aldrich with a stack of intimate fan letters she wrote to stage star Meredith Landers. Initially Jenny submits to Repellen's demands, but when the threat of scandal mounts, she kills herself with poison rather than embarrass her prominent, wealthy Long Island family. Her suicide note reveals that she was being blackmailed, and her husband John, her parents, Veronica and Artemus Todd, and her sister Lydia inadvertently make themselves the center of a police murder investigation by trying to cover up the circumstances surrounding her death. Suspecting Landers of complicity in the blackmail scheme, Lydia's fiance, Charley Warren, a lawyer, lures Landers to his home and confronts him. Landers, however, insists he does not recall receiving letters from a woman named Jenny Aldrich, but is sure that if he had, his valet, Jaffrey, would have burned them. After threatening to continue the blackmail, Repellen visits the Todds. John knocks Repellen down, and he suddenly drops dead, apparently from a heart attack. John, however, believes he is responsible for the death, and he and Artemus dispose of the body, but are seen by a stranger, who calls the police. The stranger is a small town undertaker named Chester Blodgett. Police detective Lieutenant Valcour holds off arresting John until he has gathered more evidence. The Todds, meanwhile, take a trip on their yacht, the "Amberjack," and force Landers to come with them. Valcour arrives by seaplane and, while he searches the yacht, Landers is stabbed to death in his cabin. Valcour catches Charley stooped over the body and holding a butcher knife. Believing a family member committed the murder, Charley takes the blame. Valcour and the family later discover Blodgett in Landers' cabin and realize he is really Jaffrey, who countermanded his employer's orders to destroy the letters. After conspiring with Repellen to blackmail the Todds, Jaffrey was enraged when Repellen planned to skip town with the profits and shot him through a window at the Todd home while John was struggling with him. A thunderclap and the sound of a falling bust covered the sound of the gunshot. Jaffrey locks Valcour and the family in Landers' cabin and takes control of the yacht. Valcour outwits him, however, and is eventually trapped.