A man is tossed from an apartment building to his death. Actually, he was dead from a variety of nasty injuries before he came crashing through the roof of a parked car. Lanie and Alexis will have a more comprehensive report once they get the body back to the morgue. Yes, we said Alexis. She's involved in a new internship with the Medical Examiner's office. Castle's worlds are colliding!
Video surveillance footage leads the team to the suspect's whereabouts. He's identified as Thomas Gage, though no record of such a man exits. This seemingly unflappable killer claims the man he killed doesn't exist either. This is literally the case when the dead body disappears from the morgue and Gage escapes through the front doors of the precinct.
Gage hacked into the police database to find an address for Tracy McGrath. Castle believes the suspect may have gotten arrested on purpose to access info on this woman, who becomes Gage's next victim. Beckett does a sweep of Tracy's house only to find Castle standing in the hallway with a black hood over his head. His partner is given her own matching hood by whoever is holding the gun to her head.
When the hoods come off, Castle and Beckett find themselves in a secret underground bunker run by the CIA. They have no idea what going on. Thankfully, a familiar face from Castle's past is there to bring them up to speed. Sophia Turner (guest star Jennifer Beals) is a smart, sexy CIA operative. She also happens to be Castle's inspiration for Clara Strike from his Derrick Storm book series.
Thomas Gage is a former CIA spy who has gone rogue. He may be trying to initiate a catastrophic event which poses an imminent threat to the country. Gage killed the agent the CIA sent after him as well as Tracy McGrath, whose day-planner includes the word "Pandora." This happens to be the name associated with Gage's mission.
Despite the objections of another operative, Martin Danberg, Sophia asks Castle and Beckett to covertly continue their search for Thomas Gage. He's all for it. She's a little uneasy about keeping secrets from her team. Beckett also admits to being taken aback by the fact that her partner "researched" with someone else before her. Castle assures her that Nikki Heat is a far more complex, nuanced character.
Tracy McGrath was a climate scientist with a PhD in applied mathematics. Castle and Beckett find her classic GTO in a long-term parking garage in Jersey. They discover a briefcase in the trunk containing a military grade spy phone and scrambler. Before they can check the last number dialed, Thomas Gage disarms Beckett with a nifty Jason Bourne-like move. He locks her in the GTO's trunk with Castle. On the bright side, at least they aren't handcuffed this time.
Castle pressed the panic button Sophia provided on his cell phone just before Gage smashed it. Beckett doesn't want to wait for his "girlfriend" to rescue them. She digs around under a writhing Castle to find a tire iron to pop the truck. When they reach the outside world, a CIA operative is waiting for them with those stylish pitch black hoods.
Back at the CIA bunker, Beckett seems disconcerted as Castle and Sophia fall into an investigative rhythm. The team learns that the person Tracy called is Dr. Martin Blakely, a mathematics professor who consulted for the agency. The guy was believed to have died in 2002. Agent Danberg says that Blakely specialized in something called a linchpin theory. He'd find a small event that would trigger a larger event. The domino effect would cause cataclysmic results.
Castle wants to crack a code involving chess pieces to determine where Tracy was to meet Blakely. Beckett is more interested in solving the murders. This leads to the two of them working separately. Don't worry. It doesn't last. Thanks to Martha, Castle realizes the chess clue has nothing to do with the game. He still needs help deciphering it. Beckett suggests he contact Sophia. Castle says, "She isn't my partner. You are." Nice.
Castle and Beckett work in perfect harmony to determine that Blakely was to meet Tracy at the Brooklyn Bridge Park. They decide to keep her date. Beckett questions Castle about how close he was with Sophia during the stakeout. Blakely arrives before she can get an answer. The formerly-deceased professor wants to be taken to Pier 32. When they get there, he'll tell them what they want to know about Pandora.
Blakely says the Pandora paper he wrote detailed a linchpin that was tied to the economy. It would cause a crisis that would bring about the end of the country as they know it. Blakely bolts from the car before revealing any real details. BANG! The professor is gunned down by an unseen sniper.
CRASH! A black truck with tinted windows slams into the back of the car. It guns the gas pushing Castle and Beckett towards the edge of the pier. SPLASH! The car goes head first into the water with Castle and Beckett trapped inside. Better hold your breath. This one's TO BE CONTINUED.