The Ponderosa becomes a war zone when it is invaded by a detachment of Mexican mercenaries under General Diaz. The general is furious when one of his men, Forsythe, disobeys his orders to get a hostage peacefully, and instead shoots Little Joe in the back. Diaz forces Ben to lead his men over the back roads of the Ponderosa, so they can ambush a gold train led by Emperor Maximilian's men.