In the powerful conclusion of a two-episode story arc, when the FBI fails to get his daughter back, Castle takes matters into his own hands, reaching out to a shadowy fixer to help him recover Alexis. But Castle soon learns that his daughter's kidnapping may be part of an even more sinister agenda.

When the murder of an Army veteran puts Beckett on the trail of the man who shot her, Castle must decide how much he's willing to sacrifice to keep her safe. As secrets are revealed and feelings are put on the table, the lives of the detectives at the 12th Precinct may never be the same.

Kate Beckett's investigation into her mother's death is reactivated when Hal Lockwood - a professional hitman with knowledge of Beckett's mother's murder - stages a spectacular escape during a court hearing. As police launch a manhunt for Lockwood, Castle and the team uncover evidence of a deeper conspiracy involving a mysterious figure with law enforcement connections who is linked to both Lockwood's escape and the killing of Johanna Beckett. The search for Lockwood and the quest to identify his co-conspirator leads to a shocking and deadly conclusion.

In the first of a two-episode story arc, Castle and Beckett begin a murder investigation that also exposes a plot to kidnap the daughter of a wealthy Middle Eastern businessman. FBI Agent Harris, an even-keeled professional is brought in to help find the kidnappers.

In the show’s 100th episode, Castle finds himself in the unfortunate position of NOT being able to work a case. While he’s holed up in the loft with a broken leg, Beckett goes off to investigate the death of an IRS agent without him, leaving Castle miserable and bored. But when he thinks he witnesses the murder of a young woman in the apartment across the street, he is thrown into a "Rear Window"-esque murder mystery that hits much too close to home.

With time running out, Castle and Beckett must put aside their differences with Agent Fallon to avert a city-wide catastrophe.

Federal Agent Jordan Shaw, an insightful and accomplished Federal investigator teams up with Castle & Beckett to hunt down a cunning and elusive serial killer.

When the detective who investigated Beckett's mother's murder is shot before Beckett's eyes before he can give her new evidence in the case, Beckett's old wounds are reopened. The investigation of the detective's death leads the team to an old scheme which may provide the answer to why Beckett's mother was murdered and who ordered it. Beckett and Castle's relationship takes a new turn.

While investigating a shocking ritualistic murder, Beckett and her team uncover surprising evidence linking Castle to the killing. As the evidence against him mounts, loyalties are tested. And when surprising revelations come to light, Beckett begins to wonder how well she really knows her new lover and partner of four years

Picking up the morning after, Castle and Beckett now have to decide if they're a couple or was it just a onetime deal. But before they can tackle that, they must deal with those responsible for Kate's mother's death who are now a threat to Beckett.

A crew of bank robbers disguised as classic television doctors take hostages which include Castle and Martha. But things are complicated by the fact that Beckett's on the outside having her every move scrutinized by a hostage negotiator and Castle's on the inside with information that the hostages are just a distraction for a more ominous plan.

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

In the second part of the story begun in "Tick, Tick, Tick," the serial killer remains at large and is taunting Castle, Beckett and Jordan Shaw to catch him

A secret investigation conducted by Beckett related to her mother's murder goes awry when a man she has been surveilling is killed. When evidence links Beckett to the victim, she and Castle become the targets of a manhunt that puts both of them in grave danger.

When Castle's novel ''Heat Wave'' becomes a movie, actress Natalie Rhodes accepts Beckett's invitation to visit and learn about the character she will play; Natalie observes Castle and Beckett's investigation of the murder of a matchmaker.

Castle and Beckett arrive at a crime scene to discover that the female victim bears a shocking resemblance to Medical Examiner Lanie Parish. As the team tries to make sense of this mystery, they realize the killer may be targeting detectives of the 12th Precinct. Dr. Kelly Nieman, an exclusive Manhattan cosmetic surgeon who draws Castle and Beckett's interest because of her connection to the victim.

Castle and Beckett pursue a ruthless killer who, they discover, is part of a sinister, international conspiracy. Castle and Beckett are joined on the case by Sophia Conrad, a smart, sexy CIA operative who has a complicated past with Castle.

Castle and Beckett investigate the apparent robbery-homicide of a New York cab driver, only to discover that the victim was involved in a mysterious conspiracy with unimaginable consequences. As the stakes continue to rise, hard-charging federal agent Mark Fallon takes over the investigation. Together, Fallon, Beckett and Castle must race to unmask the truth about the victim before it's too late.

A grisly murder investigation leads Castle and Beckett to a suspect who claims he's traveled back in time to stop terrible events from unfolding, events that will change the course of human history. Is he simply a deluded killer, or is it possible that he's telling the truth?

Castle and Beckett’s plans for a romantic weekend in the Hamptons are interrupted when a dying man stumbles into Castle’s backyard, collapsing into his pool. Unable to escape the lure of the investigation they join up with the small town’s well-intentioned, but inexperienced sheriff to find the killer,

In the season finale, an interview with a high-profile federal law enforcement agency forces Beckett to reconsider what she wants out of her job and out of her relationship with Castle. Meanwhile, the body of a young woman is found floating inside the water tank of a skid row flop house, but as the team investigate, they discover that her final resting place is just one of many strange things about her death.

When a beautiful woman is found dead in an alley, all clues point to her being a victim of the notorious Triple Killer. The Triple Killer, or 3XK, terrorized New York City four years ago, then mysteriously disappeared. Now he's back. In a deadly battle of wits, Castle and Beckett race against time to stop 3XK before he claims his next victims.

Nothing is as it seems when Castle and Beckett investigate what appears to be the assassination of an intelligence operative. Meanwhile, Beckett's romance with Demming threatens her relationship with Castle, forcing them to confront their feelings for each other.

While investigating the shooting death of her ex-partner in New York, Beckett comes to believe the suspect has fled to Los Angeles. Against orders, she travels to L.A., going renegade to track down the killer, with Castle unexpectedly along for the ride. As they dig deeper into the motives, they uncover a trail that leads from a rooftop pool in Hollywood to the sandy beach of Santa Monica. Along the way, they visit the set of the "Heat Wave" movie (based on Castle's book) and enlist the cast to help break the case. But as they get closer to apprehending the killer, Castle begins to wonder whether Beckett is out for justice or revenge.

While investigating the death of an Irish mobster, Beckett and Castle uncover a local turf war that may be connected to both a late-night infomercial guru and an international drug smuggling operation. But the case turns agonizingly personal when evidence emerges that the killer they're chasing may have had a hand in Beckett's mother's murder.

Castle & Beckett race to find the "Linchpin" in order to stop the first domino in a chain of events which will plunge the United States into war. Their efforts continue to put Castle in contact with Sophia Conrad - a smart, commanding and sexy CIA operative who was Castle's inspiration for Clara Strike in the "Derrick Storm" series of books; and intelligence officer Martin Danberg is back.

When Castle and Beckett wake up in bed, handcuffed together, in a locked room with no memory of how they got there, they must piece together the mystery of where they are and why, all while trying to escape. But as the two of them adjust to being shackled together, what's the biggest threat they face... the people who abducted them or each other? Meanwhile, Ryan, Esposito and Gates are left to investigate their disappearance in a case where all is not what it seems.

Alexis enlists Castle’s help on an Innocence Review case to prove that a death row inmate, Frank Henson, was wrongly convicted. With only 72 hours left before his execution, Castle and Alexis (with help from Beckett) urgently investigate the original murder, only to uncover explosive secrets that may seal Frank’s fate.

Castle and Beckett investigate the murder of a dockworker turned bar owner who's body is found floating in the East River. In the process of the investigation they uncover a secret buried since the days of Prohibition.

Stakes rise as the 12th Precinct matches wits with serial killers Jerry Tyson (3XK) and Dr. Kelly Nieman. With the clock ticking, Castle and the team must crack the case before the killers claim their next victim.

A wealthy museum patron is a suspect when a valuable sculpture is stolen. Castle and Beckett investigate the theft with the help of an insurance investigator who sets her sights on Castle.

Beckett is recruited to assist on a Narcotics investigation, but a routine mission turns deadly when an undercover operation goes awry. To survive, Beckett must engage in a battle of wits against some of the most dangerous men in the New York underworld – including a powerful enemy from her past.

When a bomb explodes at a protest rally killing five people, Castle and Beckett realize the key to solving the case is to reconstruct the 47 seconds prior to the explosion. Using video and witness accounts, they uncover the shocking truth about who planted the bomb.

When Castle and Beckett discover that the victim of a building fire was actually shot to death, they get on the trail of a serial arsonist turned murderer. Meanwhile, Ryan's wife, Jenny, goes into labor, but disaster threatens to ruin the joyous moment.

While investigating the mysterious shooting death of a young woman, Castle and Beckett face a cop's worst nightmare when they discover that the gun used in the killing is Det. Ryan's old service weapon - the one that was stolen by the serial killer, 3XK. Now with the clock ticking, the team must work to solve the murder, track down 3XK and retrieve Ryan's gun before the killer strikes again.

Last season ended with Beckett wrestling over whether to take a high-profile job in DC -- a dilemma made more complicated when Castle proposed to her. In the Season 6 Premiere of "Castle," Castle and Beckett will deal with the consequences of their decisions against the backdrop of a high-stakes investigation.

When Castle and Beckett investigate the killing of a treasure hunter, they discover the case is linked to a mysterious homicide from 1947 involving a hard-boiled private detective. Castle realizes the only way to solve the present-day murder is to solve the murder from the past. The 1947 case comes to life through stylized flashbacks, featuring Castle as the private eye and Beckett as a femme fatale.

The murder of a young record store clerk takes a strange turn when the team discovers his past history as a high-level hacker. But it's nothing compared to the shock Castle receives when their investigation leads them straight to his father, Jackson Hunt.

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.

With tensions rising between Castle and Beckett, Castle finds himself a new partner -- Detective Ethan Slaughter (guest star Adam Baldwin, "Firefly"), a tough and colorful cop from the city's gang unit. But Castle gets more than he bargained for when Slaughter shows him a grittier side of police work that puts Castle in the line of fire like never before

Detective Beckett fights for her life as Castle, plagued by guilt over his role in the events, struggles to uncover who's behind her brutal shooting. Meanwhile, back at the precinct, Ryan and Esposito have to adjust, as Victoria "Iron" Gates becomes the precinct's new uncompromising Captain.

Beckett's life is on the line when she steps on a pressure sensitive bomb. While the team searches for a way to disarm the explosive, Castle distracts Beckett by arguing with her about who fell for whom first.

When an ex-con is mysteriously slain in an alley, Castle and Beckett believe a vigilante is behind the murder. But efforts to identify their suspect are thwarted when they discover that he roams the city in a Superhero costume – and may indeed be a Superhero. Can they capture and unmask the killer before he strikes again?

Castle's latest theory is alien abduction after an astrophysicist's death is found to be from explosive decompression. A well know alien abduction expert gets involved in the case. To complicate things more, a government agent wants to shut down their investigation.

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.

Castle and Beckett investigate the murder of a missing plastic surgeon who is found dead in the front seat of his car after a week of being parked curbside. As they delve into the twisted world of surgery obsessed patients and secret operations, Castle experiences a fatherly rite of passage as Alexis attends her first prom. And while looking into Beckett’s past, he unearths information that could end his relationship with her forever.

When a man is found dead in an industrial cake mixer, Castle and Beckett trace the murder to an Irish gang in Staten Island and a beautiful bar owner named Siobhan O’Doul. Much to everyone’s surprise, Detective Ryan has a complicated history with Siobhan and the Staten Island crime family from his days working undercover in narcotics. When the case hits a dead end, Ryan must go back undercover to expose the killer, complicating his relationship with his wife.

It was longtime Castle friend Mayor Weldon's political clout that allowed Castle to partner up with Beckett. But now, when a woman is found dead in a car that traces back to the Mayor's motor pool, that partnership comes under fire as the scandal surrounding the investigation threatens to bring down Weldon's administration.

A desperate young murder suspect, Emma Briggs, takes hostages at gunpoint then mysteriously insists that she will only negotiate with one person: Richard Castle.

When Beckett and her team burst into an apartment on a murderer's trail, they see Castle standing over a dead woman's body holding a gun; Beckett arrests Castle as he asserts his innocence.

Castle and Beckett uncover that a bullet is missing from the crime scene while investigating what happened when an art dealer was gunned down in his own gallery. However, when it turns out there was a witness to the murder, they need to refresh the man's memory, only to find out that he suffers from amnesia and can't even remember who he is.

While doing some investigative work at a New York mansion, a prominent ghost hunter is murdered. Castle and Beckett must figure out if paranormal activities are to blame.

When Castle's idol, a famously reclusive author, turns up dead, Castle is determined to solve his hero's murder. But as he and Beckett dig deeper, they discover that truth is stranger than fiction.

When a body is found in the theater of Martha’s latest show, Castle and Beckett’s investigation leads them into the unexpectedly dangerous world of competitive a capella.

When Richie “The Pitbull” Falco, a larger-than-life personal-injury attorney is found dead, Beckett and Castle investigate the many clients and competitors who had motive to kill him. But the mystery deepens when they discover a shocking secret that may be linked to Richie’s murder.

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

When the body of a local college fraternity student is found gruesomely murdered, Castle has to go undercover as a professor in order to gain access to the victim's world. However, he and Beckett soon discover that behind the fun and games of college are some darker secrets the university wants to keep hidden.

When Sid Ross, the powerful creator of a long-running sketch comedy show is killed, Castle and Beckett are called to investigate. But as they delve into the victim’s life and the colorful world of “Saturday Night Tonight,” they uncover a shocking secret that may explain Sid’s murder.

With their best lead in hand, Castle and Beckett are ready to take on LokSat. But an unforeseen twist puts their case – and their lives – in jeopardy.

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

After a movie star turned theater actor is mysteriously killed, Castle and Beckett go backstage and learn the star had more to worry about than just his lines.

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.

Castle takes on a routine P.I. case, but the investigation turns deadly when he witnesses a murder.

Detective Kevin Ryan is on the security detail of a charismatic congressman attending a charity event when shots suddenly ring out. Driven to apprehend the killer, Ryan must revisit the events that led up to the shooting, with the help of Castle and Beckett.

A mysterious recurring dream drives Castle and Beckett to seek answers about the two-month period when he went missing. But their search for the truth has deadly consequences.

Beckett's side of her abrupt disappearance is revealed. After receiving a mysterious tip from her past, Beckett is launched into a fight for her life, with a team of mercenaries hot on her trail. While Castle investigates why his wife is on the run, Beckett must figure out who wants her dead, before they can finish the job.

After a man is mysteriously murdered in a park, Castle and Beckett team up with a competitive, high-powered female detective from Hong Kong, who has information about the victim. But as Beckett digs deeper into the case, she realizes neither her Hong Kong colleague nor the victim may be quite who they seem.

When a recruit officer at the NYPD Academy is killed, Beckett and the team go back to their old training ground to investigate. Meanwhile, Castle must reckon with a decision with profound consequences for him and Beckett.

When an astronaut, training for a trip to Mars, is mysteriously killed inside a Mars simulation, Castle and Beckett don spacesuits to investigate. But when they discover no one inside the sealed simulation could have committed the murder and no one from the outside could get in, the case takes a shocking turn

Detective Slaughter returns to enlist Castle’s help in solving a high-stakes robbery case. But when a body is found linked to the crime, Slaughter becomes the number one suspect in the heist turned murder, while Castle has to determine whether he’s guilty or help to prove he’s innocent.

The murder of a man connected to smuggling Turkish relics sends Castle, Beckett and the 12th Precinct on a search for a stolen antique believed to be Aladdin’s lamp, in hopes that it can lead them to the killer.

In order to hunt down the brutal murderer of a grifting seducer, Castle & Beckett must investigate New York’s elite. Meanwhile, Castle plans to surprise Beckett on their one-year wedding anniversary.

After Hayley does a favor for an old friend, she finds herself implicated in a killing and cyber-terror attack. Now, Beckett and Castle must rush to solve the case and clear Hayley’s name.

A clue at the scene of the death of an armored-car driver leads Beckett and Castle back to an old case solved by Esposito. But complications arise when they learn that Esposito might not have been telling them everything about his past with the culprit.

As Castle and Alexis travel to London, their routine flight turns deadly when the plane’s Air Marshal is found murdered. With the help of Beckett on the ground, Castle and Alexis race against time to find the killer before he carries out his fateful plan.

When Beau Randolf, the founder of hit adult video franchise "College Girls Gone Crazy," is murdered, Castle and Beckett are confronted with a lengthy list of husbands, fathers and ex-college girls who all have motive. So to find the killer, they must delve deep into the victim’s life, where they find surprises at every turn. Also Alexis starts a video blog, but Castle is not happy that personal and intimate details about her life are being made public.

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

When the star of Castle’s favorite ‘80’s action movie is mysteriously murdered, Castle and Beckett delve into the victim’s secret past and pursue his killer with help from a team of aging action heroes.

Castle returns to the City of Angels in search of answers about his missing time. But things take a deadly turn when he’s recruited by the legendary Greatest Detective Society to help solve a murder.

Castle finally gets his day in court when he takes the stand as the key witness to a murder from five months ago. But when new information suddenly arises, he and Beckett must race against the clock to prevent a miscarriage of justice.

When the son of a Russian diplomat turns up murdered, Beckett and Castle find themselves in a dangerous game of international crime and punishment, with Castle having to entertain a jovial Russian security officer who winds up more involved than anyone planned.

When a teenaged boy whose family has recently fallen on hard times is found dead in a boat in Central Park, Castle and Beckett must piece together the mystery behind the boy's final moments. Meanwhile, Castle mulls over leaving Martha home while he chaperones Alexis' trip to Washington, D.C.

When an axe-wielding, escaped psychiatric inmate drops dead in Castle’s P.I. office, Castle and Beckett’s investigation leads Castle to suspect the victim’s death could be the work of the Antichrist.

When an up and coming DJ is killed at a pop star's album release party, Beckett and Castle must dive into the raucous world of New York's music industry. Then, when the investigation leads to a troubled teenager, Esposito takes the kid under his wing, hoping to put him on the right track before it's too late.

When a priceless work of art is stolen and its transporter murdered, Castle and Beckett must work with the key witness to track down the painting and sniff out the killer.

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.

When an ER physician is gunned down in the street, Castle and Beckett soon discover that the victim was a mob doctor to a Mafia family run by an old friend of Castle's. Also, against this backdrop of Christmas, Esposito and Lanie reach a defining moment in their relationship.

When a mild mannered safety inspector for the city miraculously survives a poisoning, it might be luck; but when he survives another, it’s a mystery Castle and Beckett will have to solve.

A man is killing people and posing them in Vodun (Voodoo) tradition. Castle's ex-wife announces her plans to move back to New York.

Castle and Beckett delve into the world of extreme sports when a mysterious motorcyclist shoots an up-and-coming professional skateboarder.

When a body of a young woman is found inside the dryer at a laundry room, Castle and Beckett uncover that the young woman worked as a nanny in the upscale building. Meanwhile, as Castle works on his "Nikki Heat" novel series he watches Beckett's actions as she works the murder case.

The investigation behind a body found wrapped in a rug on the sidewalk leads Castle and Beckett deep inside the world of New York City politics. The partners discover a world of expensive escorts, arrogant tycoons, corrupt investigators, and the effects of betrayal.

When Odette Morton, a contestant on the hit competition show “A Night Of Dance,” is found murdered in her dressing room, Castle and Beckett must navigate the case’s many twists and twirls without stepping on each other’s toes. But as they delve into Odette’s past, they discover that this reality starlet was harboring a shocking secret that may have led to her death

While the team investigates the murder of a toy company CEO, Castle uncovers a lead to his mysterious disappearance, launching him into a dangerous investigation of his own.

Castle and Beckett get an inside look at the cutthroat world of the New York fashion industry when they investigate the brutal murder of a young model during Fashion Week.

When an ice cream vender is shot, evidence leads Beckett and Castle to believe that an unknown second-grader may have vital information about the case. Castle goes undercover at an elementary school to try and identify the second-grader but nothing goes as planned.

When a web celebrity is murdered, Castle and Beckett explore the flashy world of internet fame. But when the killer posts pictures from the crime scene on a photo-sharing site, they realize they are up against a social media sociopath who may strike again.

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.

Castle and Beckett investigate the murder of a Wall Street trader, but the case takes a shocking turn when the they discover the victim was an undercover informant for the U.S. Attorney’s office. To complicate matters further, the U.S. attorney involved is Elizabeth Weston, Captain Gates’ estranged sister.

When a famed relationship therapist is murdered, it appears that her access to the secrets of her elite and powerful clients led to her death. But when Castle and Beckett discover the victim was in possession of a rare object worth millions of dollars, they realize that this case may be even more complicated – and dangerous – than they thought.

Beckett and Castle search for a psychic's killer while debating the existence of extrasensory abilities.

Beckett is called to an accident scene to find Castle's car in a ravine, engulfed in flames.

A robbery-homicide prompts Beckett to invite Demming to assist on a case, giving Castle a ringside seat to their budding romance. When it becomes clear that the two men have very different ideas about how to proceed, the investigation becomes an unspoken competition for Beckett's attention, one in which each man races to solve the case, as Beckett referees between her two admirers.

A documentary crew follows Castle, Beckett and the team as they investigate the murder of a rock band's lead guitarist.