Lewis and Hobson are looking at the body of Vicki Walmsley as a theft of etorphine is reported by the Garsington Equine Centre. The drug was last used a year earlier on a horse that hurt its teenage rider, Joshua, the brother-in-law of Reuben Beatty, the first murder victim. Joshua's mother Jane ends up admitting that she saw Reuben on the day of his murder. Polly, Reuben's wife, hands over her husband's appointment book, which reveals an unknown client who went by the initials of ‘K.D.' Lewis and Hathaway look through Crane's files and find a vital clue that leads them towards the murderer.