When a psychopath commits murders based on novelist Castle's books, Detective Beckett seeks his help to solve the case. He decides to work with her and uses his experiences as research for his novels.
Starting over isn't easy, especially for John Nolan who, after a life-altering incident, is pursuing his dream of joining the LAPD. As their oldest rookie, he's met with skepticism from those who see him as just a walking midlife crisis.