British Army deserter Thomas Collins is working with the Texas Rangers in Galveston to secure a supply of gunpowder, which is desperately needed back in San Antonio for the continuing struggle against the fearsome Comanche Nation. Unfortunately, Thomas's past catches up with him in the form of a ruthless British army officer, Captain Speirs, who has been sent across the Atlantic to apprehend him. As Collins and the Texan Lawmen slowly drive their heavily laden wagons back to San Antonio, they are relentlessly hunted by Speirs and his men, attacked by the forces of a powerful former president of the republic who wants the gunpowder for himself, and harried by a Comanche war party. Thomas has to take command of the Rangers to ensure they reach San Antonio safely, but faces some tough decisions when his lover Sarah is kidnapped by Speirs.