In pre-CastroCuba James Wormold (Guinness), a vacuum cleaner salesman, is recruited by Hawthorne to be the Havana operative of the British secret service. He creates agents from men he knows by sight, and he sketches "plans" for a rocket-launching pad based on vacuum parts to increase his value to the service and to procure more money for himself and his expensive daughter Milly. Because his importance grew, he was sent more operatives from London to be under his command. It becomes much harder for him to maintain his facade when they arrive. However, when they do, all of his imagined information begins to come true. His "agents" are assassinated and he is left with a serious problem. He admits what he's done to his secretary, and he is recalled to London. Rather than risk the story leaking to the press, they bestow honors on Wormold and offer him a position teaching espionage classes in London. He decides to marry his secretary, Beatrice, and his daughter Milly consents.
Production
It was actually filmed in Havana. The new Cuban government was willing to have a movie made that showed the corrupt old regime along with meddling foreign spies.