The murder of a 15-year-old schoolgirl and the apparent suicide of her boyfriend lead the investigation to the discovery of sex parties where under-age girls are procured for politicians, businessmen, Oxford dons and policemen which in particular make the sifting of evidence very difficult. Endeavour's superior, Detective Inspector Fred Thursday, recognising he is a detective he can trust, takes him under his wing and Thursday is determined to break the case and bring it to a successful conclusion together with Morse.