In the spring of 1942, the New Zealand government presents the U.S. a 70-year-old wooden twin-masted schooner. The US military decides to use the ship to place spies ashore behind Japanese lines. While underway, the ship is commanded by Lieutenant Rip Riddle of the US Navy; while in port, the ship is commanded by Major Simon Butcher of the US Army which leads to many disputes between the two men.