Secret Agent Matt Helm must recover a stolen 'helio-beam' with the power to destroy the earth.

As part of his plan for world conquest, archvillain Julian Wall has kidnaped Dr. Norman Solaris, the inventor of a helio-beam, a device capable of destroying the earth by harnessing the sun's rays. Wall has also eliminated most of America's ICE (Intelligence and Counter-Espionage) agents, including the famous Matt Helm. Unknown to him, however, the ever-resourceful Helm is alive and traveling incognito. Arriving on the Riviera, Matt finds his contact woman murdered, but he meets Solaris' daughter, Suzie, who is worried about her father's disappearance. Matt poses as an American gunman on the lam; and Wall hires him but becomes suspicious when Matt rescues Suzie from being killed by one of Wall's henchmen. Matt and Suzie escape and make their way to Wall's island stronghold. After numerous misadventures, they rescue Dr. Solaris and destroy Wall and his gang, thereby preventing the imminent destruction of Washington, D. C., by the helio-beam.