British expatriate Jim Wormold (Alec Guinness) runs a vacuum cleaner store in Havana, Cuba. He has promised his vain daughter, Milly (Jo Morrow), a horse and a country club membership, which leaves him desperate for money. When Hawthorne (Noel Coward) proposes he become a paid British agent and recruit other spies, he accepts, and haplessly embarks on a new career. Though he's delighted when he meets gorgeous fellow spy Beatrice Severn (Maureen O'Hara), Wormold finds he's now a target.