A group of 21st-century colonists inhabit an underwater city called Pacifica. Originally intended as a purely scientific installation, the U. S. government wants to stash all its gold reserves from Fort Knox there, along with a fantastic new radioactive element. The brother of Pacifica's returning former commander plans to steal the gold and on top of that, the city faces destruction by an asteroid from outer space!

Dean Martin stars as an amiable gunrunner in this tongue-in-cheek western. Martin teams up with fugitive-from-justice Alain Delon, a Spanish nobleman engaged to the beautiful Rosemary Forsyth. Amidst several Indian attacks, hairbreadth escapes, and wild chases, Martin does his utmost to steal Rosemary away from Delon.