Bronco, a contract Army Scout, is escorting Amy Carter to Fort Monument where her husband, a captain, is the commander. As they come over a rise and see the fort, it appears devoid of life but Bronco sees a large war party of Comanches behind them. He whips up the team to race to the fort where the doors open to let them in. The fort is manned by five men led by Sgt. Ross. Everyone else has been killed by the Comanches, they have no horses and little water but enough ammo for a few days. Bronco agrees to abide by Ross's decisions since they are under siege. At her request Cpl. Rod Evans escorts Mrs. Carter to see her husband's unmarked grave. Chief Black Leg and another brave approach the fort under a flag of truce. Bronco rides out to meet them but Ross shoots the brave before Bronco can talk to Black Leg who he knows. He is forced back to the fort where the soldiers say another brave was about to shoot Bronco. A suspicious Bronco decides to search the fort and stumbles on a find ...