Test pilot Tuck Pendleton volunteers to test a special vessel for a miniaturization experiment. Accidentally injected into a neurotic hypochondriac, Jack Putter, Tuck must convince Jack to find his ex-girlfriend, Lydia Maxwell, to help him extract Tuck and his ship and re-enlarge them before his oxygen runs out.

Kate Capshaw plays a schoolteacher and suburban housewife who happens to be an ex-spy. Nobody knows of Capshaw's previous espionage activities, least of all her somewhat obtuse husband Cliff De Young. When Capshaw's ex-lover Jeroen Krabbe, an intimate of Castro, lands in a Cuban prison, she is swept back into the spy business, leaving her nonplussed hubby in the dust.