In 1876, tired of empty promises of a Land Treaty with the Whites, the Comanche and Kiowa tribes join forces to go on the warpath and forcibly evict all the settlers from their lands. Normally, the Comanche and Kiowa tribes are enemies but decide to put their differences aside for this aim. In the Buffalo Valley region, a U.S. Cavalry troop under the command of Capt. Dave Storm is tasked with the evacuation of white settlers from the area. In order to avert a war with the Indians, Capt. Storm seeks a last-minute pow-wow with the Comanche Chief Growling Bear and the Kiowa Chief Black Eagle but he can only obtain a two-day delay before the Indian attack. Comanche Chief Growling Bear is a man of his word but Kiowa Chief Black Eagle intends to break it. Black Eagle is determined to follow the withdrawing white settlers and attack them while crossing the only withdrawal route through Thunder Pass.The Thunder Pass route seems to be a safe bet since most Indians avoid it due to an old Indian superstition that says the pass is evil. Capt. Storm gathers most settlers from the area. Among them are Tulsa and Ancient, two gold prospectors, the Hemp family, Miss Murdock, an embittered young widow, Bergstrom, a mysterious St. Louis skin trader and travelling salesman Daniel P. Slaughter. Capt. Storm's military escort is comprised of Army Scout Injun and three troopers, Barnett, Reeger and Rogers. The departure point for the whole group is Chicataw Mesa stagecoach stop. As they prepare to leave, the stagecoach arrives but the driver has been killed by an Indian arrow and the sole passenger is gravely wounded and unconscious. Capt. Storm decides to bring the wounded man along, on a litter, despite the group's protests. Capt. Storm suspects the wounded man to be Dalstead, a U.S. Government envoy, en route to the Comanche and Kiowa tribes with a new Peace Treaty. He keeps this fact a secret from the others who think the man is just an illegal gun-runner, selling rifles to the Indians. On the way to the pass, the group experiences acts of sabotage by an unknown party, and an attempt by Bergstrom to kill the wounded man on the litter. Also, open acts of rebellion against Capt. Storm's authority and decisions are initiated by Bergstrom, who secretly signals a group of pursuing Indians. The chances of the group to reach Thunder Pass and safely make it across to Fort Terahawk seem very slim.