Castle and Beckett investigate the death of a student studying the sociology of bondage.
Tropes:
- Blackmail: Matt was Jessica's rival for a research fellowship. When he found out that she was working as a dominatrix, he threatened to tell her boyfriend if she didn't withdraw her fellowship application. He's not the killer.
- Distracted by the Sexy: Esposito is flustered by the dominatrix he's trying to interview, who manages to get him on his knees struggling to unlace her boots. Ryan, happily in a relationship with his Honey Milk, is cool and collected and, offscreen, manages to unlace the boots in seconds.
- Fanservice Extra: When Castle and Beckett first walk into Mistress Irina's House of Pain, we're treated to a lot of brief clips of beautiful people in latex.
- Laser-Guided Karma: Matt had blackmailed Jessica to withdraw her application for a fellowship he thought he deserved more, and later dropped off her copied research at her apartment, which resulted in her death. At the end, Montgomery implies that Matt not only got denied the fellowship, but booted out of his program for his actions.
- Naughty by Night: Jessica leads a double life as dominatrix Mistress Venom.
