Matt Helm is called out of retirement to stop the evil Big O organization who plan to explode an atomic bomb over Alamagordo, NM, and start WW III.

Rance Roden plans to kill off all the buffalo and thus cause the Indians to riot. After they destroy the US Cavalry, Rance and his gang will take over the West. Meanwhile, a Boston magazine gets wind of the buffalo slaughter and sends editor Kenneth Cabot and his associates to Casper, Wyoming to investigate.