When a young woman is found dead under circumstances described exactly in a book written by acclaimed author Richard Castle, he is brought in to provide insight into the case. When more victims turn up in similarly-accurate conditions described in his books, Castle is enlisted to assist the investigation by applying his knowledge of criminal behavior and his own books to the department's considerable skills.
The body of a nanny stuffed into an apartment building clothes dryer sets off a convoluted investigation into the hows and whys of her death. Castle, now a part of the detective team through an arrangement with the mayor, lends his skills of envisioning scenarios and pointing out seemingly-unrelated details - not to mention unorthodox methods - to the investigation.
The shooting death in Central Park of a boy from a rich family sends Castle and Beckett into the world of New York private academies, where circles of friends prove to be almost more conniving, evasive, and mysterious than they can fathom.
When a prominent politician is murdered, the Department finds itself under intense pressure from the city government to explain what happened. However, the squeaky-clean politician had another side he had kept carefully hidden from the public.
The discovery of a hard-frozen body at a construction site leads the investigation of her death into unsolved cases from years past, tangling Beckett and Castle's case with a missing-persons case that was closed but never really solved.
Someone is not just killing, but doing so ritualistically. Castle's knowledge of obscure rituals points to someone conducting a findsman's ritual; whatever he or she is doing, it's obvious that something has been lost and they want it back. However, trying to find the truth amid illegal immigrants and confusing facts tests the abilities- and imaginations- of the team.
When a member of New York's high society is found murdered and stuffed into a small wall safe, the Department is put under pressure to get to the bottom of the story. But to get the answers to the string of robbery/murders, places must change; rather than Castle visiting New York's dark alleys, Beckett must follow him into the world of glitz, glamor, and, ultimately, murder, after they discover that the robberies are only connected by the victims having attended a specific charity event.
While unusual circumstances are practically usual, a body drowned in a bathtub of motor oil has the team scratching its collective head. But the mystery only deepens when investigation shows that the victim may have been involved with a crime more than 20 years old and was working with (or being stalked) by a true crime writer. Behind the scenes, the relationship between Castle and Beckett finally rears its truly competitive head during a high-stakes poker game involving New York's legal system elite.
The disappearance of a young child has the team scrambling for answers when additional help arrives in the form of FBI agent Will Sorenson who, among other things, is an ex-boyfriend of Beckett's. As Castle butts in on the investigation despite instructions to stay out, friction is inevitable (Particularly since the case that brought Beckett and Sorenson together ended with the death of the victim).
The gruesome murder of a plastic surgeon sends Castle and Beckett into a confusing world of cosmetic surgery, unstable patients, and the witness protection program. But when Castle discovers additional information about Beckett's past, it could end up fracturing the partnership.