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Season 4, Episode 16
Air date February 20, 2012
Written by Andrew W. Marlowe
Directed by Rob Bowman
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"Once Upon a Crime"
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Linchpin is the sixteenth episode of the fourth season of Castle.


Castle and Beckett realize what that Linchpin is. They are working with Sophia Turner, the CIA agent who was Castle's previous muse. In their attempts to prevent a war from breaking out, they are betrayed by someone they thought they could trust. Over the course of the investigation, Castle begins to learn more about his father.


When we last left our intrepid heroes, the mysterious Professor Blakely had identified a "linchpin"—an event that, if allowed to happen, would trigger a series of events ending in the end of America as we know it. But before he could tell Castle and Beckett what specific that was, he was murdered and Castle and Beckett's car pushed, with them, off a pier.

In the sinking car, Castle and Beckett are racing against time to escape before they run out of air. The doors won't open and Beckett must have dropped her gun. Fishing underwater, Castle finally finds the gun and shoots out the rear window, allowing them to swim to the surface. At the surface, Esposito vents his frustration about not knowing what's going on. He has a security clearance of his own, and yet he can't know but Castle can? Also he's happy they survived.

Then the CIA arrives and collects Castle and Beckett. Sophia is furious that not only did they crack the code and not share the information, but that they got their best lead killed. She mostly ignores Beckett but gives Castle the chewing out of a lifetime, saying that he's "the same reckless, immature, self-centered jackass that he always was". She says that he's endangered the country with his actions and that he can't just re-write the ending like he did with their relationship in his books. She bitterly sends them home. In the elevator, the cherry on top of his crap sundae is that he has to admit to Beckett that he slept with her. She wonders how many other "muses" Castle has had.

When they get back to the precinct, they find out that the feds had thrown the NYPD off the crime scene and shut the investigation down. They have no idea what was at the pier that Blakely wanted. Lanie reports that the CIA got a court order in record time and has Blakely's body now, too. Still trying to work the murder case and catch Wheeler, Ryan reports that investigations of Blakely are a dead end so far. Castle realizes that they still have one lead: Blakely played chess, so who did he play with?

Beckett and Castle continue bickering about Sophia, now in front of Lanie. Beckett can't stand that they had a history and even slept together. The conversation gets both bitter and explicit, and Castle gets another cherry on top of his crap sundae when he realizes that Alexis was standing behind him and heard the whole thing. Alexis pesters Castle all the way home to find out who Castle's mystery girlfriend was; she guesses correctly that it was the mysterious federal agent that collected him at the docks. Castle sends her to bed, and walks into his office, but finds that there's still one person at the CIA who believes in him. Sophia.

She faked her diatribe against him. The decision to include him in the mission had been politically controversial, and she had to be seen shutting him down. Plus, having him officially off the case let her use him to stay on the case, unofficially. Sophia knows that Castle will keep digging, that he's driven to know how the story ends. She calls up Castle's secret file on Beckett's mother's murder as an example. She explains that the CIA hit the same dead end with Blakely, but did find one lead at the pier. Blakely had stashed a go-bag with ID's, money, and plane tickets. It also had a list of accounts, which Sophia gives to Castle. She tells him to be careful, because she does still care about him.

The next morning, Beckett is doing paperwork when Castle arrives, coffee in hand. Gates won't issue Beckett a new car until she files an incident report, but she can't because the incident was classified. So she's stuck at the precinct while Ryan and Esposito canvass chess parks. That duo are discussing the case, wondering what's really going on. Esposito had friends in Special Forces who worked intelligence cases. They all died. Finally, one chess player recognizes Blakely. He was a crazy player, who made strange and bizarre moves but always won in the end. The player points them to the player he was closest to, a man named Janacek Spivey.

Beckett's run down the account number Sophia gave them. Two million dollars in secret consulting payments from aid groups, environmentalist nonprofits... and the think tank that gave him the Pandora assignment. One million dollars, half six months ago and half last week when the project was completed. Both payments came from offshore accounts that have since been closed. Another dead end.

Esposito gives them the rundown on Spivey. Two time national chess champion and economics professor. He's done considerable consulting with the IMF, UN and US Congress. In interrogation, Spivey says he was an incredible chess player, seemingly anticipating his every move. They talked about economic theory and macroeconomic models in detail—it seemed like Blakely knew more than Spivey about economics. Spivey also knows where Blakely lives, and Beckett races off to his apartment in Ryan's car.

In the apartment, they find two things of interest. First, a "room of crazy" where Blakely has events and connections strewn everywhere, connected by strings that represent connected events. The room is a spiderweb of economics, science, and geopolitical events. At one end, the outcome of it all: World War III. At the other, a picture of a little girl. The other thing of interest is Thomas Gage, who walks in and stops Castle from calling the CIA. He tells them to run, and the reason why is obvious when a grenade is shot into the room's window. It explodes behind them, destroying everything except the picture of the little girl, which Castle took. A machine gun rips through the apartment from across the street, as Gage tries to lead them to safety. Castle has a million questions, but Gage points out (not knowing Castle) that they can have answers or they can live.

Gage explains that he didn't kill Blakely or McGrath. He's the good guy, trying to stop Pandora, but he doesn't know who the Pandora target is. So far, Gage has figured out that the people who hired Blakely are connected to military/industrial organizations in Eastern Europe who want to trigger Pandora. He also knows that they have help within the CIA. Whoever this mole is, he's setting up Gage as the fall guy for when Pandora happens. Beckett seems to believe him, but it's too late. The doors of Gage's van are forced open and a response team has them covered. Sophia has finally caught Gage.

Turner and Danberg don't believe a word of what Gage has said. Beckett points out that if he really was a rogue agent, that he should already know what the linchpin is. Turner points out that he probably does know, and was faking it to win their trust so he could figure out how close the CIA is to stopping him. As a trained intelligence agent, lying convincingly is his job. The attack was similarly staged to win their trust, so Gage must have allies. Turner questions Gage himself, but he continues to stick to his story that he's been set up.

So it all rests on finding out who the girl in the photo is. Computer searches are running up empty, so they try asking Gage again, hoping he'll change his tune. He does: he's been shot to death. Sophia puts the whole building on lockdown, while they track down the mole. He was covered by cameras, and the video feed had been hacked to hide the murder. Tracing the hack, they discover there is a mole in the CIA... Danberg. He denies it, but then takes a staffer hostage, gets into the elevator. They immediately freeze the elevator and open the doors, but he's already vanished.

Sophia blames herself. In retrospect, it's obvious. He was the one who'd discovered Pandora, and had been the one to draw most of the connections in the case. He'd been the one to expose Gage, and even had tried to have Castle and Beckett shut out of the case. Who knows what other moles might have been working with Danberg? And they're back to square one. They can't find the girl in the photo, and without knowing who she is they can't figure out what's going on. Castle makes the breakthrough... if they can't find the girl, search for the landscape behind her. If they can figure out where she's from, they can narrow down who she is. Sophia is elated, calls Castle a genius, and kisses him on the cheek. The begin a database search to locate the mountains in the photo. It'll take a while.

Castle goes for coffee and Beckett has time to ask Sophia about their relationship. Sophia liked Castle, once. They'd been intensely attracted to one another from the start, but when they finally slept together, the air went out of their relationship and they were left with all the things that drove them crazy about one another. Sophia sometimes wishes that they'd never slept together, so they could have kept what they had.

Much later that night, they finally locate the mountains and, shortly thereafter, the girl. She's the daughter of Xiang Ganghong. Mr. Ganghong is close to the finance minister, very influential in Chinese policy. While he often works with the US's enemies, he supports China's purchase of US national debt. If he were killed, he would simply be replaced. If his daughter died in what he thought was a botched attempt by the US government to kill him, then he might be able to change Chinese policy to end their purchase of US debt.

The US government spends far more than it takes in as taxes. To finance the government, it borrows trillions of dollars, mostly from China (this isn't actually true; see note below). If China stopped financing the US government, then the government would shut down and austerity measures would be put in place. Economic collapse would result. Without financing, the US military wouldn't be able to stop America's enemies from attacking its allies. Multiple wars in the middle east, in Taiwan, the end of the era of American global supremecy. What's worse is that Xiang Ganghong landed in New York City an hour earlier with his family.

Turner doesn't know who she can trust in the CIA. The NYPD probably isn't involved, but there's no way they can stop CIA assassins. Notifying the Chinese is out—the outrage and scandal could trigger the linchpin on its own. The only people in Headquarters that Sophia trusts is Castle and Beckett. She seals up the headquarters so that any other moles are isolated, and calls another unrelated team that she has on standby. The three race to the McKinley Building to stop the linchpin.

They arrive to find Sophia's backup team already in place. But Danberg's there, too. He was seen entering almost an hour before but they haven't found him yet, and don't know who his partner is. As they walk, Castle notices that they're heading for a room in the parking deck, not the lobby where the assassination will take place. He turns and Sophia's got a gun on him. Her partner disarms Beckett. Even now Castle doesn't understand what's happening, and Beckett has to put the pieces together for him.

Turner is seemingly the mole. She was the one who was seemingly arranging the Pandora event. The agent with them is her accomplice, who she seemingly sends upstairs to kill the girl. It was Sophia who seemignly killed Blakely and McGrath but no proof is given, to cover the operation. Turner put the blame on Gage, and then later when he died she put the blame on Danberg. Her man won't quite make it in time to stop him killing Ganghong's daughter. Gage or Danberg, it doesn't matter—the Chinese will still trace the murder back to the CIA, causing the dominos to fall. Castle still can't believe that Sophia Turner would betray her country, no matter what the paycheck. Talking in Russian with an American accent, she answers that she isn't even an American.

And she seemingly needed to kill Castle, too, once he was on the case. She knows him too well, he'd never stop investigating until he knew the whole story, and eventually would figure it out. So she'll seemingly kill him and Beckett—they'll die heroically trying to save the little girl from Danberg. Castle's father will be proud. Oh yes, Castle's father. He's the reason why his type of novelist got such intimate access to the CIA. She's surprised that he didn't already know this, but now he'll never seemingly know. A gun fires, and Sophia falls to the ground, seemingly dead. It's Danberg. Once he was implicated, he realized that the mole was calling the shots. Like Gage, he went rogue to realize what was going on and stop Pandora from happening. And they've got only seconds to go. Beckett and Danberg run off, but Castle is paralyzed by the betrayal and heartbreak and sits there, staring in horror at the lover who seemingly so utterly betrayed him. The family is entering the building, but before Turner's partner can seemingly shoot, Danberg tackles him and drags him outside. They're surprised and confused, but shrug and continue their trip. It's as though nothing has happened.

In the 12th, Danberg, Castle, and Beckett are circling up over coffee, closing up the case. Esposito wonders to Ryan what he thinks it was all about, and Ryan smiles knowingly and says, "You mean they didn't tell you? Huh..." In the room, Danberg explains that Langley believes that Sophia was probably a former KGB sleeper agent, that when the Soviet Union fell she'd have been abandoned and simply continued her cover. But when seemingly contacted by an an unknown group telling her to continue her mission and earn a fortune, she seemingly went into business for herself. Beckett asks if they know who hired Sophia. Danberg says he doesn't and even if he knew, he wouldn't tell them. Danberg claims not to know anything about Castle's father, but he has fished Beckett's car out of the river and are returning it "better than new".

Castle is still wondering about his father, but Beckett reminds him that Sophia told a lot of lies. She's not to be trusted. She knows it must be hard having been betrayed by Clara Strike, but Castle tells her that in the end, Clara was more like Beckett than Sophia. "Smart, fierce kind... I think that's why I was drawn to you... as a muse." The two wonder if there was really anything to the whole linchpin theory. Beckett doesn't know if she really saved the world or not, but she did save a little girl, and that's enough for her.



Main Cast

Guest Cast


Castle: That whole sinking car thing? Much cooler in movies than it is in real life.
Beckett: And for the record, I prefer watching spy thrillers to being in them.
Beckett: slept with her.
Castle: Yeah, yeah. Yeah, I slept with her.
Beckett: Have there been others?
Castle: Women?
Beckett: Muses.
Castle: No. Why?
Beckett: I just wanted to see how big the club was that’s all.
Esposito: So what do you think this was all about?
Ryan: You mean they didn't tell you?
Esposito: What? Th...
Ryan: Huh.
Esposito:Th—they told you?
Alexis: And I thought the dead bodies were going to be the grossest part.
Castle: Funny. Good night.
Alexis: So, who’s Beckett talking about?
Castle: None of your business. Now go to bed.
Alexis: The woman at the docks. Who is she?
Castle: Nobody. Now go to bed.
Alexis: I saw the way you looked at her. She’s not nobody.
Castle: Well, it doesn’t matter who she is, because I’m never going to see her again. Now go to bed.


  • During his time in Army Special Forces, Esposito had frequent access to Top Secret information. Several of his buddies in the service volunteered for intelligence missions. They all died.
  • There's a Fear Factory song called Linchpin from Digimortal album, just like the episode's title.
  • Castle says in "Pandora" that this is just like a Jason Bourne movie, except that the CIA are the good guys and the rogue agent is the bad guy. This episode reveals that the plot is actually exactly like a Bourne movie.
  • While credited as Sophia Conrad, she is referred to throughout the episode as Sophia Turner. No in-story explanation is given. Both names imply her eventual role: Conrad sounds similar to "comrade" (a term commonly used to refer to communists in fiction), while Turner refers to "one who changes sides". Indeed, the inconsistency itself references Sophia's ambiguous identity.
  • Sophia tells Beckett that she enjoyed an unresolved sexual tension with Castle when they worked together; however, the magic was gone after they slept together and she wishes in retrospect that they'd never consummated the relationship.
    • As Beckett points out, Sophia told a lot of lies. This may have been a malicious lie intended to drive a wedge between Castle and Beckett. This theory is supported by the fact that the spin she puts on the relationship is very different depending on whether Beckett is around or not.
    • Sophia's tale is a cautionary tale that plays on the fears of both Beckett and Castle. Beckett fixated on Turner's account of the relationship losing its magic once it turned sexual. For Castle, Turner was a former muse with whom he had a serious relationship who had never loved him, and was just using him and laughing all along.
    • It's also a form of commentary on the arc of the show itself. Executive Producer Andrew Marlowe has repeatedly been guarded about whether or not Castle and Beckett should ever actually enter a relationship. He's often asked about the "Moonlighting Curse", where the show fell apart shortly after the two main characters finally hooked up. Here, through Sophia, he explicitly describes the problem of having the two characters sleep together.
  • Beckett is inclined to believe Gage's story because he didn't know what the linchpin event was, but Turner argues that he did know, and had faked not knowing to win their trust so he could figure out how close the CIA was to catching him. Later, it turns out that this is exactly what she had been doing. Being seen tracking down the linchpin also had the effect of giving her a plausible excuse to be there when the assassination happened.
  • The mystery of Castle's father, mentioned occasionally in passing since the beginning of the series, takes a new twist as Sophia claims that Castle's father is a CIA agent (or someone higher up the chain of command) who pulled strings to help get Castle access to the CIA for his novels. If true, this implies that Castle's father knows who Castle is.
    • While it's possible that this was simply a lie, by this point Sophia thought that Castle was moments from death, so a motive is less clear.
    • For the first time, Castle appears genuinely interested in exploring the mystery of his father's identity.
    • This is later learned in "Hunt".
  • Sophia's last words to Castle are in Russian, a language he doesn't know. However, Beckett speaks Russian like a native, as seen in "Deep in Death".
  • The economics professor/chess champion who played against Dr. Ballard has as his given name the surname of a Czech composer, Leoš Janáček.
  • A "go-bag" is a term for a small pack of supplies. In a case of emergency, the go-bag has everything you need to escape a disaster. The Department of Homeland Security recommends that every American keep such a kit, since in the event of an emergency DHS can't have relief crews in place until 72 hours after a disaster. Blakely's variation is designed to evade capture rather than escape a disaster.
  • The premise of the episode is that if China stops financing the United States's federal debt, a chain reaction will result in the end of American dominance in the world. However, while China's holdings of US treasuries are significant compared to other foreign investors, they only hold a small percentage of the total US debt (7%), which is held by investors in dozens of countries. The vast majority of the US national debt is held by Americans.[1]
    • The victim's father is identified as being close "to the ruling party". However, as a Communist nation, all parties except the ruling party are illegal. The ruling party is the only party. [edit: This is not quite correct. Other political parties exist in China. But they have no real power.]
    • Xiang Ganghong's name is incorrectly listed. In China, surnames come first.
  • Agent Danberg, in gratitude for Castle and Beckett's help, didn't just fish out and repair Beckett's car: he also installed undisclosed "improvements" in it.
  • So far, it's revealed that Castle and Beckett told Ryan about their mission, making Esposito really furious.
  • Although Alexis kept asking who Sophia was, Castle got annoyed and wanted to change the subject.