Munitions maker King Bendigo is the wealthiest man alive, and what the King wants, the King gets. What he wants is the investigative powers of Ellery Queen and his father, New York homicide detective Richard Queen, in order to investigate some threatening letters. Bendigo has an enormous security apparatus in place that is capable of dealing with threats that involve sovereign governments, but these threats are more personal. Ellery and his father are transported to the Bendigo private island and soon determine that the threats originate within the King's family. The King has two brothers, his assistant Abel and drunken sot Judah, and the King's beautiful wife Karla completes the list of suspects. Judah makes little secret of the fact that it is he who has originated the threats; he announces that he will shoot King at exactly midnight on June 21st. At that time, King is locked in a hermetically sealed room accompanied only by his wife; Judah is under Ellery's observation and armed only with an empty gun. At midnight, Judah lifts the empty gun and fires -- and King falls back, wounded with a bullet. Karla falls under suspicion but no gun is found on her person or anywhere in the room; similarly, Judah cannot have had a bullet in his possession, having been searched repeatedly. When Ellery learns that the Bendigo family is originally from his familiar haunt of Wrightsville, he travels there for an investigation of the King's early life. Upon his return to the private island, he solves the crime and dramatic and deadly effects follow in short order.