Wendy Dupree, murdered in a cheap motel, wrote a clue in her blood. When Castle realizes it's no word but a number, it leads, in combination with her phone records, to a storage compartment about to be auctioned, previously rented by Wendy's brother Wendell, an ex-con who died in a suspicious accident a few months earlier. He was employed as a driver by socialite Anjelica Henley, who recently reported a valuable diamond stolen in a robbery, focus of further criminal intrigues. The earlier past provides the crucial clues, while Castle and his mother worry about Alexis's impending moving out to a dorm in Columbia.
- The Butler Did It: Castle is delighted he can finally say this.
- Couldn't Find a Pen: The first victim wrote a clue in her own blood.
- Twin Theme Naming: Wendall and Wendy Dupree.
