Castle goes undercover as a professor after a college fraternity student is killed in a grisly manner. During the investigation, he and Beckett unearth some sinister secrets the university wants to keep suppressed.
A seductive con man is killed, and the investigation has Castle and Beckett questioning New York City's upper crust. Meanwhile, Castle has a surprise in store for his and Beckett's one-year anniversary as husband and wife.
Det. Slaughter returns seeking Castle's help in a robbery case. However, Slaughter becomes a suspect when the heist case turns into a murder case, and Castle's unsure about whether his pal is innocent or guilty.