Artistic License – Economics: Boy, do the writers of the show not understand how economics and the US debt actually WORK. China currently owns less than 10% of our national debt. While China suddenly stopping to buy US debt would be a moderately big deal, in reality all it would really cause would be a slight uptick in inflation of the US dollar. Even if Beckett stating that so-called 'austerity measures' being imposed were true, it would not suddenly result in our military being gutted and totally unable to respond to threats, as she claimed, and would certainly not start a war.
Artistic License – Physics: It takes a very long time for Beckett's car to fall to the bottom of the river. At the edge of the river. Where it should be shallow.
Boom, Headshot!: Gage gets a pistol directly to his forehead.
Dutch Angle: Gage's interrogation has him filmed upright, but Sophia at an angle, foreshadowing her role as the traitor.
Evil All Along: Sophia Turner turns out to be the mole behind Pandora's plot. She framed Gage because he figured out who she was & had him killed to prevent telling the truth.
Foreshadowing: Sophia reveals that Castle had access to the CIA thanks to his father, one season before Hunt.
Frame-Up: Martin is initially revealed as the mole, but it turns out he was the good guy trying to stop Sophia who was trying to have the daughter of a Chinese politician who had economic ties to the United States killed in order to start World War III.
The Gadfly: At the end of the episode, Ryan pretends he was in on the story the whole time to mess with Esposito.
Hollywood Economics: China buying up US debt has been a right wing talking point for years, but China calling it in couldn't cause an economic collapse. That's not how international finance works.
Hollywood Law: Averted this time with the CIA. Because one of the people they're investigating is a US citizen, the CIA can't investigate.
Layout of a Season: Each of its three full seasons has a major two-parter with a big guest star representing a federal agency right about this time. In this season, we have "Pandora" & "Linchpin", guest starring Jennifer Beals, playing a member of the CIA & Soviet operative.
Pulling the Thread: Sophia lampshades that Castle always has to do this, which is why she has to kill him and Beckett.
Rogue Agent: Gage learned that someone inside the agency was a traitor and had to go off the reservation to prevent WWIII.
Room Full of Crazy: Blakely's apartment has photos, articles, String Theory... all of it justified because he was a high-level genius whose theories were predicated on tracing events that can trigger giant results. His room is tracking the linchpin that will trigger WWIII.
Sacrificial Lion: Ultimate badass Gage is killed offscreen to show that someone on the inside is betraying the country.
Smart People Play Chess: Blakely scouted a globally influential economist by playing chess in the park.
Title Drop: Both "Pandora" and "Linchpin" are dropped multiple times after Castle and Beckett learn about Blakely's work.
Wham Line: "My father?" "You don't think you got special access to the CIA because of your charm."
