The settlers commanded by Captain Shields are trapped in Dead Man’s Gulch by Comanche warriors, and after suffering heavy casualties and running short of water and ammunition, they send Jim Gibbons to Fort Adams with a desperate appeal for immediate assistance. Colonel Greaves dispatches one hundred cavalrymen under Lightning Jo, a renowned scout celebrated for his speed, strength, horsemanship, and tracking ability, who becomes even more determined when he learns that Lizzie Manning is among the besieged travelers. Lizzie, Egbert Rodman, and the remaining defenders use their wagons as a barricade while Lightning Jo guides the relief force through ambushes and deception, but continued attacks reduce the defenders to only a few survivors with no ammunition left. Just as Swico-Cheque and his Comanches launch their final charge, Lightning Jo and the cavalry reach the gulch, drive off the attackers, and save Lizzie, Egbert, and the other survivors from almost certain death.