Sir Alec Guinness gives one of his most unforgettable performances as Professor Marcus, the mastermind of a gang of vicious bank robbers who rent a room from elderly widow Mrs. Wilberforce (Katie Johnson, winner of the British Academy Award for Best Actress). But when the dear old woman begins to meddle in their "perfect crime," the crooks (including Herbert Lom and the legendary Peter Sellers in his first major screen role) decide that she must be killed. Now after a daring heist, a runaway parrot and several cups of tea, can the most diabolical criminals in London still manage to murder one sweet old lady?