Based loosely on the poem by Rudyard Kipling, this takes place in British India during the Thuggee uprising. Three fun loving sergeants are doing fine until one of them wants to get married and leave the service. The other two trick him into a final mission where they end up confronting the entire cult by themselves as the British Army is entering a trap. This is of the "War is fun" school of movie making. It has the flavour of watching Notre Dame play an inferior high school team.

At a British army post in India, native water carrier Gunga Din dreams of becoming a soldier. When the regiment learns that the telegraph wires to one of their outposts have been cut, Sergeants Cutter, MacChesney and Ballantine are sent to investigate. The three sergeants find the compound in the hands of a fiendish band of killers known as the Thugges, members of a fanatic religious order that worships the goddess Kali and has sworn to annihilate the British in India. The sergeants fend off the fanatics' attack, and upon their triumphant return to the post, Ballantine announces that he is foresaking the army to marry Emmy Stebbins and take a job in a tea company. His announcement is met with consternation by his pals, who immediately begin to scheme to keep their buddy in the service. Meanwhile, Gunga Din leads Cutter, who is obsessed with discovering hidden treasure, to a temple of gold, which, they discover, is the holy shrine of the Thugges. As he decoys the Thugges, Cutter sends Gunga Din to the post for reinforcements. MacChesney uses Cutter's dangerous position to trick Ballantine into reenlisting in the rescue mission, and the two ride out, leaving Ballantine's sweetheart behind. The sergeants have misunderstood Gunga Din however, and believing that Cutter is being held captive by priests, arrive with no reinforcements. Captured by the Thugges, the three sergeants watch helplessly as the Scottish troops march in to the fanatics' ambush. Then Gunga Din, imbued with the soldier's spirit, realizes his dream by sounding the bugle to warn the troops, heroically sacrificing his life for his sense of duty. Saved by Gunga Din's warning, the British defeat the Thugges. Later, Ballantine decides that his place is in the army, and Gunga Din is appointed a corporal in the British army and is buried with military honors.