The plot follows Connington's recurring detective Mark Brand (known on the radio as "The Counsellor"). Brand matches wits with a highly meticulous killer who has set up a metaphorical "Maginot Line" consisting of four distinct legal and physical roadblocks to shield himself from the gallows:
First Defence -- The victim's body is burned beyond recognition inside a blazing car so authorities rule it a simple suicide. Second Defence -- If the police suspect foul play, the clues are engineered so the actual killer's identity remains completely obscured. Third Defence -- If the killer is identified and brought to trial, he has evidence prepared to prove he did not commit the specific charge brought against him. Fourth Defence -- If his true guilt is later uncovered, he exploits the "double jeopardy" loophole, ensuring the law cannot try him twice for the same crime.
