Mike, Chip, and Larry are three lusty, brawling U. S. Cavalry sergeants stationed in Indian Territory in 1870. Mike and Chip are determined to prevent Larry from carrying out his decision to leave the Army at the end of his current hitch and marry beautiful Amelia Parent. One night the three cronies befriend a trumpet-playing former slave, Jonah Williams, who dreams of someday becoming a trooper. A tribe of fanatical Indians begins terrorizing the area, and the headstrong Chip decides to attempt the capture of their leader. Accompanied by Jonah, he sneaks into the Indians' secret meeting place while they are conducting one of their mysterious rites, but he is discovered and taken prisoner. Jonah, however, escapes and races back to tell Mike and Larry. When Larry insists upon going to Chip's rescue, Mike makes him sign a reenlistment paper "just to make his help official" and promises to destroy the paper after the mission. Mike, Larry, and Jonah make their way to the Indian stronghold, but they too end up as prisoners. As the Cavalry rides into a trap where a thousand warriors are waiting to ambush them, Jonah blows the regiment's favorite tune on his trumpet as a warning. The ensuing battle ends in victory for the Cavalry; the three sergeants are decorated, and Jonah is made a trooper. Thinking himself discharged, Larry drives off in a buggy with Amelia, but the crafty Mike shows the post's commanding officer the reenlistment paper he had promised to destroy. Larry, it appears, will be forced to serve another hitch with Mike and Chip.