The owner of a private hospital is found murdered in his car, after a series of anonymous threatening letters. Suspicion falls on a retired book-maker whose daughter suffered severe brain damage as a result of negligence during an operation some years before.
Morse spends a lot of effort in investigating the possibility that the dead man was criminally negligent, and concludes that he was. While he does his best to bring the killer to justice, Morse does not seem very troubled that at the end of the day he is unable to nail him.
In Wales an experiment terrifies the local villagers.