Castle and Beckett chase a murderer who seems to be a costumed superhero.
This episode contains examples of:
- An Arm and a Leg: Lone Vengeance, or rather, Tony Valtini, cuts off Tyler Faris' hand before slicing him in half.
- Artistic License – Biology: Cutting someone in half horizontally would be hard enough, bisecting them vertically? Being an experienced butcher doesn't mean you can cut through a dozen bones and a quarter ton of meat in a single slice.
- Asshole Victim: Tyler Faris certainly gets this status for being a rapist. Even his own mother isn't horribly shocked to see him on the coroner's slab.
- Chekhov's Gunman: Two from the murder scene. The first is a New York Ledger reporter named Paul Whittaker; the second is officer Ann Hastings.
- Defrosting Ice Queen: Iron Gates doesn't quite like Castle, but she's willing to let Beckett let Officer Hastings get away with being Lone Vengeance, so long as Lone Vengeance never, ever graces these city streets again.
- False Flag Operation: A local crime boss frames Lone Vengeance for the murder of the informant tipping her off, knowing the police would automatically pursue the superhero.
- Foil: Paul and Ann reflect Castle and Beckett. Ann has a dead father and is a badass cop to Paul's romantic writer/artist.
- Freudian Excuse: Lone Vengeance's father was killed some time ago, leading her to become a police officer.
- Half the Man He Used to Be: The killer's MO on Tyler Faris, splitting him vertically in half. Castle even mentions the trope word-for-word.
- Karma Houdini: Lone Vengeance turns out to be a police officer named Ann Hastings. The new Chief refuses to press charges lest the department be embarrassed. The same officer reappears later in the series, so they weren't even quietly dismissed from the Department, even though they committed numerous serious crimes as a vigilante.
- Katanas Are Better: Lone Vengeance makes use of one.
- "Not So Different" Remark: Lone Vengeance/Ann Hastings tries to point out to Beckett that they both lost a close parent as kids and both want to take the law into their hands.
- Outliving One's Offspring: Tyler's mother ends up surviving her son... not that she's terribly surprised.
- Pretender Diss: Castle drops one for the writer of the Lone Vengeance comic."Trust me, he is no Stan Lee. He's not even Sean Elt."
- Pulling the Thread: Castle notes that Paul is left handed and insists on continuing the investigation.
- Samus Is a Girl: Lone Vengeance turns out to be a woman.
- Selective Obliviousness: Gates basically chooses to ignore Officer Hastings’ actions as a vigilante because it would draw unwanted attention to the precinct, arguing that so many people were going around in the Lone Vengenace costume that there’s no way for them to be sure when Hastings was wearing the costume and when someone else was doing it.
- Unusually Uninteresting Sight: Likely she figured it was just inevitable, but Tyler's mother, after seeing his bisected corpse, reacts with mild indifference.
- Vomiting Cop: Hastings claims that seeing Faris' bisected body made her "thr[o]w up [her] breakfast."
- Who Murdered the Asshole: This exchange between Beckett and Tyler Faris' mother shows just how loved he was:Beckett: (while taking out her notepad) Ma'am, I'll need the names of all the enemies your son may have had.
Mrs. Faris: You're gonna need a bigger pad.
