The Silencers (1966)

In this, the first Matt Helm movie, we see Matt Helm coaxed out of semi-retirement by an attractive ex-partner. It seems that the evil Big O organization has a nefarious plan called "Operation: Fallout." If this plan comes to fruition, Big O will explode an atomic bomb over Alamogordo, NM, and start WWIII. Only Matt Helm can stop them.