When a potential range war heats up between cattlemen and incoming settlers in the Outlet, Washington sends U.S. Marshal Jim Crown to the Cimarron Territory to quell the dispute. Assigned to Cimarron City, Crown finds that there is no law in the town, and that he will receive no help from the Army.

Crown is forced to jail his old buddy ""Bear"", accompanied by sidekick Mobeetie, and his gang of renegade cowboys, when they go on a free-for-all drunk and terrorize Cimarron. Upon their release from jail, the cowboys discover that their boss, cattleman Hardy Miller, has lost his government land lease, due to the government favoring the movement of the incoming farmers and settlers. When Miller is forced to fire Bear and his group, they promise revenge against the settlers and vow to turn the Cimarron River bloody red.

Mobeetie, a cowpoke with a cowbell around his neck, becomes a pain in the neck for Marshall Jim Crown during a heat wave, when a trainload of dynamite is stuck in the middle of Cimarron and the railroad can't move it for a couple of days.