A Policeman, A Snake & Murders Most Foul The policeman is of course undercover MI5 agent Frank Allen, this time on the trail of drugs and prostitution; the Snake is gang boss and sadistic murderer Sammy Blake. For over fifty years Blake has controlled the underworld with bizarre and brutal efficiency, but will a large London gang bring about his downfall? Frank Allen is on the case. The Death of the Two-Headed Cartel Frank, recently promoted, recently married to Sue, is content. He feels that the undercover world is a distant memory, and he can now concentrate on 'proper' police work. Then one day he is invited to see the chief constable Sir Cedrick Porter, who offers him one final mission - with a reward so tempting, how can Frank refuse? He accepts the task immediately - and then goes home to tell Sue.