In pre-revolutionary Cuba, James Wormold, a vacuum cleaner salesman, is recruited by Hawthorne of the British Secret Intelligence Service to be their Havana operative. Instead of recruiting his own agents, Wormold invents agents from men he knows only by sight and sketches "plans" for a rocket-launching pad based on vacuum cleaner parts to increase his value to the service and to procure more money for himself and his expensive daughter Milly.