The Civil War over, Captain Sam Curtis just wants to return home, but instead finds himself embroiled in a covert operation to smuggle weapons to Mexican rebels, fighting to rid themselves of Emperor Maximilian I and the French forces who have invaded their country. Betrayed and left for dead, by the ex-Confederate, Henry Fontaine, he faces many obstacles in his quest to recover the weapons and complete his mission. Aided by Sergeant Ben Boyd and the fiery Consuela Martinez, he battles bandits, the French Army and royalist guerrillas, commanded by the ruthless Colonel Dupin, before facing his enemies in a final showdown at the rebel held town of Tacambaro.