In the aftermath of introducing their parents to each other (which ended poorly), Castle and Beckett investigate the murder of a priest and go to pick up a possible witness. As Ryan and Esposito discover that Irish mob killer Mickey Dolan might be implicated in the crime, Castle, Beckett, and Leo (their witness) find themselves being chased through the Bronx by Dolan's men after being relieved of their wallets, phones, and Beckett's gun and badge.
- Beware the Silly Ones: Leo is actually a hit man.
- Childhood Friends: Mickey Dolan and the priest grew up together and remained somewhat friendly long after taking opposite paths.
- Closest Thing We Got: Leo tries to diagnose Beckett and Castle's problems, saying that he has over 1,000 hours of therapy (albeit as a patient) to ease the tensions.
- Commonality Connection: Martha and Joe Beckett bond over talking about the worries they experience from their offspring's adventures and how to cope with it.
- Covert Distress Code: Beckett lets Castle know that something's wrong by saying she and Castle should go to a baseball game with their parents, something they can all enjoy.
- Due to the Dead: Mickey honors his best friend by choosing not to kill Leo.
- Foreshadowing: Leo apparently hurts his ankle, but is able to run to the nearest hiding place with no trouble, then is claiming he's too hurt to move, an early sign he's faking his injury.
- Robinsonade: Beckett and Castle get stranded in the Outer Burroughs after midnight when they go to interview a witness and some mob thugs force them to drop their wallets and phones and some rando steals Beckett's car, leaving them on the run with no way to get out of the area and no way to contact anyone.
- Run for the Border: Members of the O'Reilly crime family are mentioned as fleeing town, or even the country, en masse over the last week. At first, this is assumed to be to avoid a turf war, but it later turns out that the actual source is a Federal investigation hoping to arrest the lot of them.
- Shout-Out: Someone steals Beckett's car. Cue a back and forth with Castle over Dude, Where's My Car?.
- Spanner in the Works: Castle and Beckett turn out to be this to Leo, who is really a hitman. He'd faked being a witness to the murder, knowing Dolan would want to avenge his old friend and would come to him trying to find out the killer's identity. His plan would have worked flawlessly, if not for Castle and Beckett showing up just before Dolan's men.
- Undying Loyalty: Although it isn't touched upon much, Dolan has three men helping him chase down Leo, even though he's planning to turn states evidence against the family, something that is apparently known by the entire mob. Either he valued those three enough not to turn them in with everyone else and they appreciated that, or they were loyal enough to him to help him out even knowing they might go to jail, with the former being more likely.
- You Are Better Than You Think You Are: Castle gets Mickey to not kill Leo by reminding him that his best friend never gave up on him, and he needs to honor his best friend's sacrifice.
