|Season 4, Episode 23|
|Air date||May 7, 2012|
|Written by|| Terri Edda Miller and |
Andrew W. Marlowe
|Directed by||Rob Bowman|
When the murder of an Army veteran puts Beckett on the trail of the man who shot her, Castle must decide how much he's willing to sacrifice to keep her safe. As secrets are revealed and feelings are put on the table, the lives of the detectives at the 12th Precinct may never be the same.
- Nathan Fillion as Richard Castle
- Stana Katic as Detective Kate Beckett
- Jon Huertas as Detective Javier Esposito
- Seamus Dever as Detective Kevin Ryan
- Tamala Jones as Dr. Lanie Parish
- Penny Johnson Jerald as Captain Victoria Gates
- Molly Quinn as Alexis Castle
- Susan Sullivan as Martha Rodgers
- Tahmoh Penikett as Cole Maddox
- Geoff Pierson as Mr. Smith
- Judith Scott as Evelyn Montgomery
- Onahoua Rodriguez as Marisol Cartagena
- Lobo Sebastian as Diego Gutierrez
- Sal Lopez as Priest
- Riccardo LeBron as Orlando Costas
- Castle: Because of everything that we have been through together! Four years, I've been right here! Four years just waiting for you to just open your eyes and see that I am right here. And that I'm more than a partner.
- Castle: Every morning I bring you a cup of coffee, just so I can see a smile on your face. Because I think you are the most remarkable... maddening... challenging... frustrating person I've ever met. And I love you Kate, and if that means anything to you, if you care about me at all, just don't do this.
- Beckett: If I care about you, Castle you cut a deal for my life like if I was some kind of a child. My life. Mine. You don't get to decide.
- Castle: You keep going with this. They're gonna decide. They're gonna come for you Kate.
- Beckett: Let them come. They sent Coonan and he's dead. They sent Lockwood and he's dead. And I am still here Castle. And I am Ready.
- Castle: Ready for what. To-To die for your cause? This isn't a murder investigation anymore Kate. They've turned it into a war.
- Beckett: If they want a war, I will bring them one straight to their doorsteps.
- Castle: Well, I guess there's just nothing I can say is there?... O.K. Um. Yea You're right Kate. It's your life. You can throw it away if you want to, but I'm not gonna stick around to watch you so um. This is uh, over. I'm done.
- Beckett: I almost died, and all I could think about was you. I just want you.
- "In My Veins " by Andrew Belle
- "All I Could Think About Was You" by Robert Duncan
- "All I Want You" by Robert Duncan
- Gaffe: In previous episodes, it was established that the Montgomerys had two daughters. In the family photo shown, though, a daughter and a son are shown.
- However, Captain Montgomery did mention "his son" in One Man's Treasure and he stated that he had "two daughters and a son" in The Dead Pool. As to why only the daughters appeared in Knockout, it may simply be that the son is older and no longer lives in the family home.
- Also, during the investigation of the burglary, Castle mentions that it's a good thing that "Evan and the girls" were away at the time: "The girls" were definitely the daughters so "Evan" might be that son.
- Johanna Beckett's tombstone reads, "vincit omnia veritas" ("truth conquers all").
- Castle traditionally spends Memorial Day weekend at his house in the Hamptons. This year, Alexis is graduating and Martha is going alone. It's unclear what Castle's original plans were other than to view the John Woo movies; even the WriteRCastle Twitter feed had mentioned that he would be going.
- Although Esposito is furious with Ryan for calling in backup, this was precisely what he and Beckett were about to do themselves when they were jumped.
- This episode has numerous references to previous episodes:
- Beckett uses the same interrogation tactic as Agent Fallon in Setup: threatening to take away a woman's children if she doesn't waive her right to remain silent.
- The argument between Beckett and Castle is similar to the argument they have in "Knockout". In both cases, Castle urges Beckett to stop investigating and the relationship is broken off. Unlike the last time, though, it is Castle who makes the decision to call things off.
- Cole Maddox beating her so easily, despite the fact that she had a gun and he did not, was foreshadowed in Pandora, where CIA operative Thomas Gage was equally casual about defeating her in similar circumstances. Actress Stana Katic later said in an interview that the fight was intentionally one-sided, as a metaphor for how powerless she is against the all-powerful conspiracy.
- Her inability to climb back up onto the roof after the fight with Maddox was foreshadowed in Kill Shot, where she was unable to climb a ladder to the roof due to the injuries sustained in Knockout.
- While Mr. Smith warns Castle to restrain Beckett, no one outside the precinct was aware that she was working the investigation or had connected it to her mother's murder. Maddox's parting line that they "know exactly who they're dealing with" could be taken as an admission that there is a mole within the 12th precinct.
- The purpose of the burglary at Captain Montgomery's house was not to remove any lingering evidence, it was to identify "Mr. Smith" so that he could be neutralized and Beckett safely assassinated. Cole's parting line could also be a reference to this mission: to identify the man who's been protecting Beckett.
- Watch for: under the wedding photo that Cole uses to identify Smith is a legal document, a series of witness statements regarding a crime.
- This is the first time that Castle and Beckett kiss "for real", not undercover. Executive Producer Andrew Marlowe has since confirmed that things proceeded exactly as the show implies: that the two did in fact sleep together.
- Although this episode finally brings Castle and Beckett together romantically, there are two caveats. As always, Beckett makes her move only once Castle has totally given up and broken off the relationship. Second, Beckett still hasn't told Castle that she loves him.
- Whilst Marisol's last name is credited as being Cartagena, Ryan refers to her as Marisol Castañeda.