James Wormold's wife has left him and he is now scraping a living as a vacuum cleaner salesman and looking after Milly, their teenage daughter to whom he is completely devoted. Milly is being educated by nuns, but Wormold has lost any faith he might once have had. At a difficult age, torn between her devout Catholicism and burgeoning sexuality Milly talks religion, but enjoys her new-found power over men who find her attractive. Her most ardent admirer is the sinister Captain Segura whose bloody reputation goes before him. Wormold is not at all happy about this state of affairs.

He is approached by a British intelligence officer named Hawthorne who offers him money to spy for his country. Struggling for money, Wormold accepts the offer - the trouble is he doesn't know the first thing about spying nor does he have any useful contacts or information. Loathe to give up his new source of income he hits on the idea of inventing intelligence and fellow agents he has recruited. However, some of the names he chooses are those of real people living in Havana. Knowing that MI6 will lose interest unless he spices up his reports, Wormold sends sketches of vacuum cleaner parts, claiming they are a secret communist nuclear base in the mountains. It's all going swimmingly till MI6 send him an assistant and wireless operator, Beatrice. Now he has to keep his misinformation from her as well as his paymasters! But when a news story reports that one of Wormold's fictitious sources is killed in a car accident the story takes a weird and dark turn. Wormold thinks the KGB must have discovered he is an M16 spy and now they too believe his reports. Way out of his depth Wormold is now on a desperate mission to save his other sources whilst not being killed himself.