List of Castle characters

After weathering the backlash from his fans and nagging from his publisher, who is also his ex-wife, Castle is requested to help NYPD Detective Kate Beckett with a murder case that copycats scenarios from his previous novels (written before "Derrick Storm" series).

Having graduated from New York City's prestigious Stuyvesant High School and Stanford University, she is a first-class investigator who has gained a reputation as a detective who is intrigued by unusual cases, although she is also known for her ability to empathize with the victims of violent crimes.

Initially finding Castle to be quite annoying, Beckett gradually warms to him as they work together to solve murder mysteries, utilizing his imagination and insight into a killer's mind and her authority and position within the police department.

Unusually mature and responsible for her age (notably a foil to Castle's immaturity), she is highly intelligent, academically motivated (she ends up attending Columbia University), and wise beyond her years.

In season five, Alexis finally chooses to attend Columbia University so as to remain close to family and friends, and lives in their halls of residence while frequently dropping into her father's loft.

In season eight, it is revealed that Alexis has been unofficially working at Richard Castle Investigations for a month; in that time, she has successfully solved a number of minor cases.

Javier Esposito (portrayed by Jon Huertas) is a bilingual (English and Spanish) detective who works in the homicide division with his partner, Kevin Ryan, as part of Beckett's team.

In "Almost Famous", it is implied that he was in the Green Berets; this point of Esposito's personal history is developed in subsequent episodes "Knockdown" and the two-episode arc "Set-Up" and "Countdown".

In the episode "Kill Shot" he displays technical knowledge of military sniping and refers to his having served in a sniper unit, implying that he received training.

In the season four finale, "Always", Esposito stands firmly behind Beckett as she decides to pursue the investigation of her mother's murder in secret because they fear that there would be other dirty cops in the precinct.

Detective Kevin Ryan (portrayed by Seamus Dever), formerly a narcotics division cop, now works alongside Esposito as part of Beckett's team.

[7] In the season one episode "Little Girl Lost", Ryan is revealed to have a new girlfriend named Jenny; she is often mentioned, and routinely calls him to check up on him, but her first appearance comes in "The Mistress Always Spanks Twice", where she was portrayed by Dever's real-life wife, Juliana.

His love life and the fact he is in nearly-constant communication with his girlfriend/fiancée makes him subject to much teasing from his partner, so when Esposito begins dating Lanie, he relished turning the tables on his friend.

In the season four finale, "Always", Ryan sides with Castle in stopping Beckett's investigation into her mother's murder in secret, feeling that not going through the proper channels will cost them.

After Castle quits, Beckett and Esposito try to catch the killer by themselves, which causes Ryan to make the painful choice to tell Gates about the secret investigation.

In the episode "Still", Gates reveals that she was aware that Castle and Beckett were in a relationship but tells them that she did not say anything in order to maintain her own plausible deniability, and she promises to continue her silence on the condition that the two be professional on the job.

He begins emergency surgery and operates on her until another doctor can take over for him and violently confronts Castle in the hospital waiting room, blaming him for Beckett's injuries.

In the season six semi-finale "Veritas", it is revealed that Smith had faked his death and had gone into hiding to find a new way to implicate Senator William Bracken, the man behind the whole conspiracy.

He is later directly responsible for the events of "Kick the Ballistics" when he hands Ryan's weapon to an enemy under the guise of friendship, knowing that the man will use the gun in a future crime and attract the attention of Beckett and her team.

He confides to Castle that he enjoys stalking his victims and planning their deaths more than actually killing them, and it is implied that when he leaves New York, he adopts the persona of another serial killer and carries out a new series of crimes under a different identity.

Despite being an unseen character until the season five premiere, "After the Storm", Bracken is directly responsible for one of the major events tied to the series's lore: the murder of Johanna Beckett.

Twenty years prior to the series, Bracken was working as an Assistant District Attorney in Manhattan when he learned of a small group of corrupt police officers—John Raglan, Gary McAllister and Roy Montgomery—who were kidnapping mobsters for ransom.

Bracken's influence is again felt in "Knockdown", when John Raglan approaches Kate Beckett looking to clear his conscience when faced with his own imminent death from cancer.

Beckett discovers that the proceeds from the drug ring are being laundered through the Future Fund, a political fundraiser collecting money to support Bracken's presidential bid.

She also learns that Bracken had ordered one of his contract killers to save her after Vulcan Simmons—the figurehead for the ring and one of the original suspects in the murder of Johanna Beckett—blows her cover, as a means of repaying his debt to her.

With her innocence proven, Beckett confronts and arrests Bracken during a televised speech in which he announces his ambition to become president, charging him with conspiracy, fraud, and the murder of her mother.

Bracken refuses to speak of "Loksat" to Beckett and after Castle's visit, attacks a guard to get sent to solitary, only to be murdered in his own cell as Ryan and Esposito come to question him.

Despite Bracken's death effectively avenging Johanna's murder, Beckett becomes obsessed with hunting down Loksat, who ultimately proves to be a man named Mason Wood.

He made his first appearance during the "Target" and "Hunt" two-part storyline when Alexis is abducted by a former KGB operative as part of a plot to lure him into the open and kill him.

Hunt becomes the prime suspect in the murder of a hacker he enlisted to assist him, manipulating the crime scene to draw Beckett's attention so that he can lead her to Gemini.