Castle and Beckett investigate what appears to be the assassination of an intelligence operative. Meanwhile, Beckett continues her romance with Demming, jeopardizing her relationship with Castle, which forces them to finally face down their feelings for each other.
A robbery-homicide prompts Beckett to invite Detective Demming to assist on the case. The investigation becomes a competition for Beckett's attention as both men race to solve the case.
A dynamic restaurateur, finds herself mixed up in the murder investigation of a former contestant in a reality TV show called Kitchen Wars. The restaurateur is a high school friend of Beckett's and she shares an attraction to Castle. Meanwhile, Beckett's relationship with Demming continues to grow.
Castle and Beckett investigate the murder of a thief. While investigating the murder they learn that Esposito may have a personal connection to the suspect's killer. In the meantime, Robbery Detective Tom Demming is assigned to the case and hits it off with Beckett, making it hard for Castle to work together on the case.moreless
Castle appears on a late-night talk show to promote his new book, Heat Wave. During a commercial break the host, Bobby Mann, whispers to Castle, "They want me dead." The next day he is found dead of natural causes and it's up to Castle to convince Beckett to investigate the case as a murder. Meanwhile, Castle is seduced by Ellie, the guest star to appear on the show the night he died.moreless
Castle and Beckett investigate the murder of Will Medina, the assistant curator of the Natural History Museum. The museum's personnel believe his death is related to the curse of the ancient mayan tombs.
The second part of the story begun in "Tick, Tick, Tick…," after Beckett's apartment is blown up it confirms that the serial killer is still alive. He taunts Castle, Beckett and Agent Shaw to catch him.
Castle & Beckett team up with the FBI to hunt down a cunning and elusive serial killer, that is playing by Castle's book "Nikki Heat".
A half-naked woman is found in a park hanging by bondage cuffs and covered in caramel sauce. It's off to the underground world of sexual domination for Castle and Beckett to look for the killer.
Castle and Beckett will cross paths with the former Yankees skipper, Joe Torre while investigating the murder of a baseball star found dead after a trip to Cuba. Meanwhile, Alexis has a genealogy project that makes Castle consider the identity of his unknown father.
Castle and Beckett investigate the murder of a dead man found in a family's house that just returned from vacations. Meanwhile, Castle is elected as one of New York's 10 most eligible bachelors.
Castle and Beckett investigate the death of an Irish mobster, but while on the case they uncover what may be an international drug smuggling operation, as well as the killer may be involved in the murder of Beckett's mother.
Castle and Beckett are called to a wedding to investigate the murder of a bridesmaid. Castle realizes that the wedding is from a former girlfriend Kyra. Everyone's feelings are compromised, since Kyra has doubts about who she is marrying, Castle's feelings may not be as objective in the case and Beckett picks up the connection between them, making her a little jealous and have poor judgement.moreless
Castle and Beckett investigate an art dealer who is shot in his gallery, but a bullet is inexplicably missing from the crime scene. Following the trail of the missing fifth bullet, the team discovers the only witness - who appears to be suffering from amnesia.
Castle and Beckett investigate the murder of a man stuffed down a garbage chute. Things get complicated when both his wife and fiancée come in to identify the body.
Castle and Beckett investigate the murder of an Assistant District Attorney. Meanwhile, Alexis confides a secret to Beckett instead of her father.
Castle and Beckett investigate the murder of a bike messenger and the past of a prominent family figures into the investigation.
Castle and Beckett investigate the murder of rock star on the rise, in which the body is found like a scene from her latest music video.
It's close to Halloween, and a man is found murdered in a graveyard - with a stick through his heart, and sporting fangs. Castle and Beckett track the murderer to a vampire cult, all the while Castle is trying on costumes for his Halloween party - costume mandatory!
A body found down a manhole leads to the lonely life of a Czech immigrant recently fired from her job for getting too close to her employer's son. Meanwhile, on the eve of launching Nikki Heat, Castle's agent has an exciting new offer for him; but if he takes it, it would end his work with Beckett.moreless
Castle and Beckett investigate the mysterious death of an Arctic explorer during an expedition. The investigation leads them in many interesting directions including Park Avenue and the CIA. Things really gets frustrating when Castle wonders if the killer is fooling all of them.
It's fashion week and Castle and Beckett get to see what happens in the background as they investigate the murder of a model.
Castle and Beckett compete against Ryan and Esposito to see who can solve their murder case first. A few twists make the two teams work together to figure things out.