Adam Baldwin guest stars as Ethan Slaughter, a detective Castle shadows while he deals with his situation with Beckett.

• Slaughter is a tough cop chasing down a murder between gangs. 
• Beckett, Ryan, and Espo are annoyed at Castle spending time with another detective.
• Slaughter takes Caste through some rough situations while they track down the murder of a kid.
• The kid was trying to prove himself to his gang and got caught up. He called his father who then killed him.
• Beckett talks to her therapist about Castle. She thinks she may have waited too long to acknowledge Castle’s “I Love You.” 
• Alexis gets her college acceptance letters and is accepted to Stanford.