Castle and Beckett investigate the murder of a Hollywood actor playing Hamlet in a local theatre production.
- Bad "Bad Acting": Zane's final moments of life involved him putting on a performance of Hamlet that left something to be desired. When the killer saw how bad the performance was, that was the final straw before she stabbed him with a quill.
- Cain and Abel: The gang speculates that El Oso's brother Hector, a successful businessman, wanted to use Zane to gain access to his brother. Then, in true Hamlet fashion, he could take over his brother's "business" in addition to his brother's place in his wife's bed.
- Chekhov's Gun: Castle's new RFID-enabled credit card ends up being used to track him down when El Oso kidnaps him.
- Chekhov's Gunman: The paparazzi at the murder scene ends up having footage of Zane meeting with a cartel lieutenant, who reveals that Zane was doing business with the drug lord El Oso.
- Method Acting: In-Universe. Naomi stays in role as Ophelia throughout her questioning by police. Castle and Ryan try to play along until Esposito snaps her out of it by threatening to arrest her.
- No Celebrities Were Harmed: El Oso is an Expy of the real life drug lord Joaquin "El Chapo" Guzman, complete with a prison break at the end.
- Parental Sexuality Squick: Castle is rather disturbed that Martha may have been sleeping with Zane. Turns out she was just his acting coach.
- The Pen Is Mightier: The killer stabs Zane in the throat with a quill.
- Shout-Out: El Oso idolizes Shakespeare's character of Macbeth and modeled his life after him, while Castle notes that he also has several similarities to Shakespeare's Richard III. El Oso's brother seems to have modeled his life on Shakespeare's Claudius (Hamlet's uncle) and El Oso's unseen wife is following Queen Gertrude's footsteps.
- Stage Dad: Due to his love of theatre, Ryan goes a little overboard with the planning for his daughter's preschool musical, to the point where the other parents fire him as director for his unrealistic proposals. And for his attempt to blackmail another parent into supporting his plans.
- Woman Scorned: Non-romantic variant. Erin only agreed to cast Zane as Hamlet because he promised to let her direct the biopic of El Oso he was planning. She was angered when Zane announced he'd replaced her as director with himself, and ended up snapping when she saw how bad he was as Hamlet.
