Freelance assassin Hawkins is contracted to blow up Sir Gregory Upshott, a prominent and pompous London businessman. By courting Upshott's spinster secretary, he learns that his target will be taking one of the firm's typists for a weekend at a seaside hotel, the Green Man. Hawkins hides a bomb in a radio, which he plans to leave in the hotel lounge. Finding out his treachery, the secretary comes to his house to confront him but is attacked and left for dead by Hawkin's assistant who, as nobody is in, hides the body next door.