"The war with Mexico serves to bring together American officer and Mexican senorita, the former all ardent and the latter defiant because of the fact that their countries are at war. Coincident with the American victory is the successful conquest by the 'gringo' of the girl's heart."

While Joel and his older ship's captain brother Mark are at sea, the latter is abandoned in Singapore by devious ship's mate Finch who, upon their return, convinces the townspeople that Joel abandoned his brother. Joel, determined to not only find Mark but to see justice done, returns the ship to Singapore.

U.S. Marine Sergeant O'Hara has his hands full training raw recruits, one of whom, 'Skeets' Burns, is a particular thorn in his side. If Burns's lackadaisical approach to the military were not bad enough, he also makes advances on nurse Nora Dale, whom Sergeant O'Hara secretly loves. Nora is oblivious to O'Hara's feelings and is attracted to the handsome 'Skeet.' But an indiscretion turns her against him, and it takes an expedition to China and a battle with a warlord's bandit brigade to sort things out among the nurse and her two Marines.