When two separate murders are committed on the same night, Castle wagers Ryan and Esposito that he and Beckett will solve theirs first. The frenzied race to catch their respective killers and win the bet leads each investigative duo to a likely suspect, only to find that they both have airtight alibis. But bizarre twists in both cases force the two teams to work together to unravel the mind-bending mystery behind each murder.

Castle has a new book agent, Paula Haas, but she talks with him when he has gotten an opportunity that may change his career. The downside is that taking the opportunity would mean the end of his relationship with Beckett. Meanwhile, an unidentified woman is found dead in a manhole.

An up-and-coming rock star's body is found in a scene that appears staged from her recent music video.

After a bike messenger, carrying a package with content that is able to free a wrongly convicted man from prison, is brutally murdered, Castle and Beckett need to investigate the case. But they are surprised to find out that the tragic death is linked to another murder case previously investigated by Captain Montgomery. Now, in order to solve the new murder, Castle and Beckett must dig deep and discover all the secrets of a prominent New York family.

A beloved former major league baseball player is found dead after a goodwill trip to Cuba. The investigation, which includes running into Joe Torre, leads the detectives into New York's Cuban community to solve the murder. Meanwhile, Alexis' genealogy project forces Castle to consider the identity of his unknown father.

A high profile chef is found frozen to death in the kitchen of a hot New York restaurant. Complications ensue when Castle and the restaurant owner, an old high school girlfriend of Beckett's, share an attraction. Meanwhile, Beckett's relationship with Det. Demming continues to grow.

During rehearsal for "Baron's All-American Beauty Pageant," the contestants are shocked to discover the body of Miss Illinois - strangled, but by whom? As Castle and Beckett delve into the cut-throat competition of the pageant world, they learn that a number suspects had motive for murder, including jealous fellow contestants, the pageant's larger-than-life millionaire sponsor, Victor Baron, and the show's host -- hedonistic TV personality, Bobby Stark.

When Castle and Beckett investigate the murder of a man with human bite marks on his body, Castle's wild theories start flying. But none are as wild as what their only witness insists happened - a Zombie attack. As the evidence pointing towards an undead assailant piles up, the team plunges into New York's Zombie subculture to find the killer and bring him in -- dead, undead or alive

When a body is found at a sci-fi convention, Castle and Beckett are warped into the heart of fandom -- a world of egotistic celebrities, diehard costumed fans and enough drama for two galaxies.

When a young woman appears to have literally been scared to death three days after watching a "haunted" DVD, Castle and Beckett delve into one of their creepiest cases yet. To make matters worse, Castle becomes convinced that he too is marked for death when he accidentally watches the cursed video.

When Castle and Beckett find giant footprints at the site of a vicious murder, the team is forced to confront the unlikely theory that Bigfoot is the killer. But as they trek into the world of primate research, big game hunting and mythological creatures, they realize that finding the man (or beast) responsible may put them on the endangered species list.

With Beckett still in D.C., Castle and the boys investigate the murder of former child star Charlie Reynolds, who rose to fame playing the lovable nerd on an early 90s High School sitcom. But the case takes a turn for the strange when Agents Beckett and McCord arrive from Washington to take over the investigation, creating competitive tension in the precinct. But why would a washed-up actor's death warrant Federal scrutiny? Whatever the reason, Beckett and McCord aren't telling. Meanwhile, Castle has to contend with a new face at the 12th, NYPD Detective Frank "Sully" Sullivan.

When a Japanese ballet dancer is mysteriously murdered, Castle and Beckett's investigation into her secret life uncovers evidence that she was killed by a ninja, and now that ninja is coming after them.

After being banned from the 12th precinct, Castle works his first case as a private investigator.

When a young actress is murdered, the investigation leads Beckett and Castle into the flamboyant world of a telenovela.

Castle and Beckett investigate the murder of a cruise ship entertainer, only to find themselves trapped at sea with the killer.

Beckett and the 12th Precinct look into the murder of an English as a Second Language student. But when the victim's class won't talk to the police, Castle goes undercover as a French Canadian immigrant and learns that the victim was more than he seemed.