While at a house party, Castle witnesses one of the waitresses stabbing a guest to death in a room upstairs. Five months later, he's called upon to testify in the murder trial, but the trial doesn't go as expected when a new defense attorney shows up and additional evidence is uncovered.
- Armor-Piercing Question: Caleb uses several during the trial to undermine Castle's initial testimony.
- Blackmail: Roger has videotaped evidence that Sadie stole a duffel bag of cash left by the CIA in Iraq to pay their assets locked in his fingerprint-locked safe and used it to force her to give him a cut. When he demanded more money years later, Sadie had her girlfriend Nina (a waitress at Roger's party) steal a champagne glass with his fingerprint on it so she could break into the safe and steal the tape. It was during the break-in that Sadie was killed by her husband in a fit of rage.
- Conveniently Cellmates: After getting thrown in jail for contempt of court, Castle's jail cell just happens to be right across from Nina's.
- Death by Woman Scorned:
- Discussed. When Nina and Sadie's affair is discovered, the prosecution uses this fact to frame the killing as a crime of passion, but this gets called into question when contradictory evidence is discovered.
- Ultimately Gender-Inverted. Sadie was killed by her husband Lloyd when she mocked him for thinking she was sleeping with Roger when she was actually having an affair with Nina.
- Enemy Mine: Despite knowing that Caleb Brown works for LokSat, Beckett ends up on the same side as him when Castle becomes convinced that Nina did not kill Sadie.
- Entertainingly Wrong: Castle assumes that Sadie wanted Roger's used glass for his DNA in order to check her daughter's paternity. What he didn't know was that Roger is infertile, and that Sadie actually wanted his fingerprint to unlock Roger's safe.
- Get into Jail Free: Castle's plan for interviewing Nina involves him barging into the judge's office and repeatedly insulting her until she throws him in jail for contempt of court.
- Girl on Girl Is Hot: Implied in the following conversation:Nina: But Sadie was all paranoid because she'd been caught cheating with other guys in the past.
Castle: Other guys? So you were her first...
Nina: Lesbian? Yes, is that a problem?
Castle: No, not with me. You should check my search history. - Mistaken for Murderer: Castle witnessed Nina trying to pull the fireplace poker out of Sadie's body and assumed she was the killer, which was reinforced by Nina running when confronted. However, after Caleb's cross-examination, he began having doubts and eventually becomes convinced of her innocence after talking to her in jail.
- Spanner in the Works: The ADA's slam-dunk case became a lot harder when Nina's incompetent defense lawyer was replaced at the last minute by the dangerously competent Caleb Brown, whose withering cross-examination tore Castle's eyewitness account of the murder to pieces.
