Herbie Hassler (Telly Savalas) and Marty Miller (Warren Oates) are American gangsters who plan to rob an opulent aristocratic home of valuable art treasures. Under the orders of crime boss Nick Marco (Cesar Romero), the duo charms Lady Fitzmore (Edith Evans), a wealthy dowager and proprietress of a monied estate. The plan is to work in collaboration with a British gang lead by Finley (Harry H. Corbett). When the time comes to initiate the big heist, the sentimental American crooks can't bring themselves to rob their eccentric but lovable hostess. They confess the plan and work with Lady Fitzmore and Lord Fitzmore (Nicky Henson) in an effort to catch their British burglar counterparts in this delightful crime comedy.