As Captain Binghamton departs for Brisbane, his torpedo boat, PT-116, springs a mysterious leak and sinks. He is forced to use PT-73, in the charge of Ensign Parker in the absence of McHale, the skipper. In Brisbane, Binghamton restricts the crew to the boat, but they are befriended by the crew of a nearby Russian merchant vessel. The Russians try to use PT-73 to smuggle Australian whiskey. In the midst of an aimless celebration in which both crews participate, two Russian NKVD officers come aboard. After mix-ups involving uniforms, Lieut. Wilbur Harkness, pilot son of an Army Air Force general officer, is found in a Russian outfit and is carted away as a spy. Parker, who has replaced his Soviet togs with the nearest uniform--Wilbur's--is forced to impersonate Wilbur and is given the rank of Army captain. Later, while in a control tower with WAC "Smitty" Smith, Parker accidentally turns on the air raid warning at the very moment a Japanese air squadron is about to make a sneak attack. For his heroism, Parker is again promoted--to Army major. When he and Binghamton are suspended in their jeep in midair by an airplane, they spot a Japanese fleet; and with an early warning, they aid an Allied victory. Parker becomes a national hero--despite the protests of Lieutenant Harkness, now released--and speeds his way to Washington to be decorated by President Roosevelt.