British murder mystery. When Johnny Matlock (Brian Worth) whisks away a cold war secret from under the noses of Berlin's top secret agents, his every move is followed on his return to England. His girlfriend Paula (Honor Blackman) is kidnapped but her handbag is discovered at the scene of the crime by the aristocratic private eye, Duke Martin (Tom Conway). Inside it he discovers the secret formula that the agents are searching for. As Johnny grows frantic for the safe return of his girlfriend, Duke Martin plays a deadly game of double bluff with the enemy agents.