Beckett and her team burst into an apartment on a murderer's trail, only to be surprised when they find Castle, whom they had not seen or heard from in months, standing over the dead woman's body holding a gun. Beckett has no choice but to arrest Castle until he proves he is innocent.
This episode shows examples of...
- Artistic License – Economics: Making a deposit of $10,000 or more means the bank is required to report it to law enforcement. Making a deposit of just under $10,000 means the bank will be suspicious, and the bank will almost certainly report it because it looks like you're trying to avoid the $10,000 reporting limit like a criminal. Multiple $9,500 deposits would have alerted law enforcement immediately.
- The Bet: Castle and Beckett make one midway through the episode after exhausting all possible connections between their three victims: if she finds the connection first, Castle stops interfering in her cases and leaves. If Castle finds it first, Beckett has to agree to take him back as her partner and consultant. Castle wins the bet of course when he figures out the motive—only for Esposito to ask Beckett how long before Castle she knew the murder was over counterfeiting.
- Brick Joke: Beckett said in the pilot that usually the person standing over a dead body holding a gun is the one who killed them. Here, Beckett comes across just such a thing with Castle holding the gun, and of course not all is as it seems.
- Counterfeit Cash: What the murder ended up being about.
- Deliberate Under-Performance: Esposito suspects Beckett figured out the counterfeiting connection between the three victims first, but said nothing so Castle could win The Bet and continue working with her. Beckett neither confirms nor denies this suspicion.
- "Eureka!" Moment: Once Beckett mentions all three victims made tons of money, it makes Castle realize that the connection: they're all counterfeiters.
- They soon figure out the culprit once they understand how it works. The vending machine worker provides the paper for the bills, the chemist washes the bills clean, and the sculptor has the plates needed to print them. All they would need now is ink, and a tattoo artist like Kitty would have the supplies for it.
- The Friend Nobody Likes: Everyone is at the 12th is pissed at Castle for a) never calling over the summer or when he got back from the Hamptons and b) unknowingly hurting Beckett's feelings when he hooked up with his ex-wife. Once he gets himself installed into the case as a consultant again, Ryan and Esposito are passive-aggressive with him the whole episode.
- Deconstructed as Castle legitimately doesn't understand why everyone, including Montgomery, is mad at him and would likely apologize if he did. Then Reconstructed as its implied the passive-aggressiveness was just to get back at him and they are happy he's back, including allowing him to think he won The Bet allowing to stay on permanently.
- Hall of Mirrors: The scene in the How We Got Here intro (and again at the climax) involves Castle surrounded by mirrors, hearing the sounds of pursuit all around him but unable to see anything but his own reflection—until a stray bullet shatters one of the mirrors.
- How We Got Here: The episode begins with Castle being chased by someone (seemingly Beckett) shooting at him, then ends with Castle and Beckett both taking aim at each other and firing. Then the scene rewinds to the beginning of the case, three days earlier, to show how events led up to this.
- Mundane Made Awesome: The solution to the scheme the three victims and the killers had cooked up. A vending machine maintenance worker, a sculptor that works with metal, a high-school chemistry teacher, and a tattoo artist used their jobs to start up a counterfeiting operation.
- Once More, with Clarity: The opening scene is carefully edited to imply that Castle's on the run from Beckett and her team, who are shooting at him. Then most of the episode is a flashback showing How We Got Here, and the first act feeds into that misdirection even further, since Castle gets arrested as a murder suspect. But by the time the episode reaches the climax, Castle and Beckett are on good terms again—so when we revisit the scene from the opening, it's clear that Castle and Beckett are working together and pursuing the real killers.
- Plot Parallel: Just as Castle is in the doghouse with Beckett for not calling her, Alexis is angry at her boyfriend for not calling her. Talking with Alexis about it makes Castle realize how much he hurt Beckett's feelings—but he also empathizes with the boyfriend's mistake and encourages Alexis to give the guy another chance. By the end of the episode, both pairs have reconciled.
- Rule of Symbolism: Castle brings two coffees, one for Beckett, representing how their partnership is on the mend if reluctantly when she agrees to let him consult on the case.
- Shout-Out: When meth is raised as a Red Herring, Castle says that "Hey, it could be meth, just like that cable show."
- Significant Wardrobe Shift: Ryan's wardrobe had been shifting to be more like Castle's, nice suits and warm patterns. With Castle taking off for the summer, ditching Beckett, he's in far more casual attire, with neither suit jacket nor tie.
- Stab the Scorpion: In the opening scene, Castle and Beckett take aim at each other and both shoot. At the climax, we find out they were both aiming at the killers, who were flanking them.
