A prominent barrister and his wife are found shot dead in a crime that has uncanny similarities to a double murder that the barrister successfully prosecuted 15 years earlier.

The Professor is asked to decipher a macabre puzzle when a doctor and her family are found dead in a grisly tableau on their living room sofa, each having died by different means. But in which order and by whom?

When an artisan baker is found dead after receiving death threats, the police appear to have an open and shut case against the son of a convicted murderer who was sent to prison thanks to the baker's testimony.

Professor T conducts a series of lectures for his students detailing a high-profile court case in which a caretaker is accused of murdering his employer; the accused was found standing over the victim's body and his fingerprints on the murder weapon, but Professor T is convinced of his innocence, bringing him into conflict with the CID team and DI Paul Rabbits as the investigating officer.

After discovering the body of an undercover police officer, the CID team blunder into a Drugs Squad operation against a major trafficker that appears to implicate one of their closest colleagues.