Beckett fights for her life after her shooting while the 12th precinct gets a new tough captain, Victoria Gates.

Sex offender ex-con Tyler Faris is found in an alley, cut in half by a sword. Faris' victim claims that a man in a superhero uniform saved her. Even Castle doesn't recognize the uniform, which is eventually identified as Lone Vengeance, the hero of an Internet site authored by Sean Elt, a pseudonym. Actually, several people prance around New York in Lone Vengeance suits. The team investigates them and Tyler's enemies, such as his former employer Tony 'The Butcher' Valtini, thus proving to Captain Victoria Gates her lack of confidence in them is unwarranted.

Gunshots, a fleeing van and a massive blood pool all point to murder, but when Castle & Beckett arrive at the crime scene, they discover that it lacks something - the victim! The investigation leads to the cutting-edge world of life-extension science, a cunning high-tech researcher, and a sleazy porn mogul who invested in a modern-day "fountain of youth." Meanwhile, Alexis finds out whether she got into Stanford.

Student Jane Herzfeld was fatally shot with the Glock service pistol stolen from Detective Ryan by serial killer 3XK. Her ex-boyfriend, Finn McQueen, has an alibi. Phone records show she was in contact with undercover narcotics Detective Seth Carver. He had forced her to inform on Chinese mob boss Clifford Lee by acting as a tutor to his son, Ben. Castle ingeniously finds some missing links through prison records.

Jealousy arises when an insurance investigator helps the team.

Castle and Beckett confront the possibility of paranormal foul play when a world-renowned ghost hunter is mysteriously murdered while investigating a haunting at a legendary New York mansion.

Castle and Martha are held hostage during a bank robbery and Beckett has to try to get them and the other hostages out.

A hotel-casino co-owner from Jersey is found murdered. The boys go to Atlantic City to investigate "and have Ryan's Bachelor party", while Beckett stays in New York.

A case involving a sniper brings back memories for Beckett of her own shooting.

Castle and Beckett wake up handcuffed together in a locked room with no memory of how they got there. Their colleagues try to retrace their steps and find them.

When a Lothario is killed, Castle and Beckett suspect that the victim's mysterious double life holds the key to his murder. Their investigation leads to a shocking twist that threatens to disrupt Ryan's wedding with Jenny.

When a woman is found murdered in her car, Beckett and her team's investigation leads them directly to City Hall... specifically to the Mayor, Robert Weldon, who happens to be a friend of Castle's, which could also jeopardize Castle's continued involvement with the NYPD.

Dog trainer Francisco Pilar is murdered after naming Best of Show at a dog show. Castle gets the Labrador he was training temporarily adopted as team mascot, and his nose proves quite useful. Airhead reality TV star Kay Cappuccio, seen leaving Pilar's room, has a motive, but was he or she spied on by the camera planted in the dog's collar. And why is there a customs undercover agent?

Castle senses a diary of a P.I from the 1940s found in the effects of a murdered modern-day treasure hunter is the key to finding the Blue Butterfly, a blue-diamond necklace. The team works out the story situated in 1947 in the same, now derelict, music club, involving murder, gangsters, and theft; they work out the true parts and identities of culprits and victims.

The department's reputation is damaged after a convicted murderer escapes custody and steals all the evidence the police have on him, and Castle and Beckett must team up with the CIA to catch him before he kills again.

Castle and 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.

Women are found dead, dressed as fairytale characters. An event years ago that led to a death connects all three women.

During recording of TV show "A Night of Dance", spoiled-rotten rich girl Odette Morton, who made it to the semi-final, is murdered in her easily accessible dressing room. Suspects include a previously knocked-out candidate who is now automatically restored, the presenter and someone he had a secret with. But evidence shows Odette's has a big secret of her own that she recently shared with some people from her past, which includes another murder.

The FBI commandeers the NYPD detectives for little more than leg work after a bomb explodes during an anti-globalist demonstration. Castle is asked by Captain Gates to help out by using his speed-reading ability and attention to detail to sifting through mountains of witness depositions. This helps the 12th precinct team get on the right track after the FBI concentrates on the wrong suspect.

A devilishly handsome detective from Scotland Yard teams up with Castle and Beckett to find the person responsible for the murder of his friend's daughter. Also, Castle and Beckett suspect Nigel, the Deputy General at the British Consulate, is up to more than just ambassadorial balls and diplomatic luncheons. Meanwhile, Lanie convinces Beckett that she needs to make a move on Castle before it is too late.

Castle finally gets Beckett, who admits so only in therapy, she may have made him wait too long when he teams up for an investigation with her colorful colleague detective inspector Ethan Slaughter, a cowboy style bulldog, who was assigned multiple decapitated Jamaican corpses from the Irish Westies gang member Brian Reilly's maverick son. Although uncomfortable with the ruffian style, gentleman sleuth Castle proves his value while they discard a simple gang war and focus on newcomer Cesar Vales's Mexican gang. Castle not only repeatedly appeals to his former team, but actually turns to them when he disagrees with Slaughter's theory as well as his bully blackmail method.

Castle and Beckett investigate the murder of a man covered in human bite marks apparently caused by a Zombie attack.

The murder of a Latino army veteran ex-con, ex-Lobos-street gang member quickly links to a break-in in the late captain's home, to steal only and all his old police files, and yields the fingerprints of the sniper who nearly killed Beckett. Castle realizes continuing the investigation will draw him back and probably cost her life by squashing his deal with deep throat. Her refusal to back down causes a break up with Castle, and Gates suspends both her and Esposito for continuing an unauthorized investigation in a case assigned to another NYPD team. Now Beckett commits romantically.

Castle and Beckett re-evaluate their relationship after spending the night together.

Beckett returns from her suspension while she and Castle keep their relationship hidden.

Wendy Dupree, murdered in a cheap motel, wrote a clue in her blood. When Castle realizes it's no word but a number, it leads, in combination with her phone records, to a storage compartment, about to be auctioned, rented by her brother Wendell, an ex-con, who died in a suspicious accident a few months earlier. He was employed as driver by socialite Anjelica Henley, who recently reported a super-valuable diamond, stolen in a robbery, focus of further criminal intrigues. The earlier past provides the crucial clues, while Castle and his mother worry about Alexis's impending moving out to a dorm, albeit in New York.

Castle and Beckett's romantic weekend in the Hamptons turns sour when a dying man stumbles into Castle's pool.

After Tessa Horton is murdered in a bizarre fashion at her apartment, evidence piles up, all pointing at Castle. He denies knowing her, let alone having had an affair, but there are fingerprints, security footage and recovered hard-drive evidence all showing he did. Although no one in the precinct can believe him guilty, they must arrest him based on the evidence. Only then does vindictive serial killer Jerry Tyson manifest himself to Castle while he is in Holding at the precinct, promising that he won't survive jail, which calls for a radical solution.

During the annual major science fiction convention, Nebula 9 - super-fan Audrey O'Neill, who finally organized a life performance starring the short-lived series' original cast as well after decade of 'webipsodes' with a nerd couple, is found dead on set, killed with a real 'space laser' (of which only two working ones were custom-made). Castle, who thinks he has better taste, is amused to find Becket was part of a college fan group. The team works out various personal, career and business motives as well as opportunities for cast and crew.

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

When Beckett and Castle pick up a witness to a murder, hired killers attack, and they lose their cell phones and Beckett's gun. They run for protection while Esposito and Ryan try to find them.

A man dressed as Santa falls from the sky while Castle and Beckett prepare for their first Christmas as a couple.

A divorce lawyer is found dead. Meredith visits to take care of a sick Alexis while Beckett is staying there due to her apartment being fumigated.

A promising DJ is murdered at an album-release party for a pop star which takes Castle and Beckett inside the drama of NYC's music industry

Soft porn tycoon Beau Randolph was strangled with a bra during a grand party to launch another College Girls Gone Crazy franchise production. He received many death threats, such as from arch-conservative Ronald Armstrong's grim prudish movement. Beau's own bodyguard Scarlet Jones, whom Javier finds irresistible, stole a memory card from his safe and was hired by children's TV production firm. Actress Tiffany Shaw also lies a lot about her disguised party presence, which is only the top of an iceberg of family and business secrets.

The victim's corpse is found burning in a barrel by a homeless man. The team finds out she worked for US Senator William H. Bracken, whom Beckett holds responsible for her mother's murder. But he seems to be the target, this time. Only Castle learns that Beckett considered holding back evidence before another clue leads the team to prime suspect Robert McManus, a mechanic who blames the senator for his son's suicide. The senator is hell-bent on holding a high-profile speech in a hotel to launch a career-crucial environmental bill.

Hannah Green, star of a reality show, is found dead at a bus stop with a knife in her back. She has bruises from being held captive for the day she went missing from the studio. The team unravels complex rivalries for parts, infidelity and spin-offs that affect both a clothing line and Margo's son Stone Gower's series project with co-star Collette's daughter, Ashley. Castle and Becket fear the captain will discover their affair after he accidentally drops Beckett's Valentine present in the wrong coat.

Hasim Farouk, a student at Columbia like Alexis, is killed by a van crashing into him while he emptied his gun into it. The team soon works out the van was used to kidnap not only Egyptian tycoon Anwar El-Masri's daughter Sara, but also Alexis, whom she attended a lecture with. FBI agent Harris' sole lead, obtained from Castle torturing the wounded van driver, runs into a dead-end. Meanwhile, the girls attempt an escape, but discover they are not where they thought they were.

After the FBI fails to get Alexis back, Castle takes matters into his own hands.

Castle is shaky after watching a DVD which predicts, in flashy amateur horror style, the exact time of death, for no apparent reason and probably by panic-caused cardiac arrest, of the murder victim, screaming in the phone, who received it. Her ex has a solid alibi and couldn't make sense of her panic about 'it'. Tracing the DVD's shipping leads to another copy recipient, killed at home similarly. Their only link is having been jurors on executed country serial killer Nigel Malloy's trial. The team heads for his home town, loved-ones and surviving jurors.

The corpse of Jimmy, a baker popular for cup cakes, is found in his industrial dough mixer. His apprentice, Todd, noticed someone in a vintage muscle car, before being sent away. The car was identified as belonging to Irish mob boss Robert 'Bobby S.' Shannon. After FBI agent Sam Walker tells the team that Jimmy was his informant, Ryan astounds everyone by revealing he had been undercover in that gang years ago. And, to save a friend, chooses to revive his alias, Fenton, and go back undercover.

Castle is home, mostly alone, in a wheelchair after a skiing accident, bored out of his wits just before his birthday. After a while, he actually picks up a pair of binoculars Alexis gave him to play Rear Window. Indeed, right across the street a foxy resident betrays her studly husband with a younger hottie. Shortly after, the cheated husband finds his rival's hat, wields a knife and seems to dispose of the corpse while she isn't seen again. Yet his NYPD team mates only reluctantly investigate and can't find any proof. Castle becomes obsessed with the possibility that he witnessed a murder, while Beckett grows increasingly upset with his mania and sets out to find out the truth one way or the other. That's when things take a surprising and shocking turn...

A woman's body is dumped outside a hospital, with her face torn open as if by an animal or wild beast. Soon, Beckett and Castle become prey for the killer.

Castle is jealous when Beckett has to protect a billionaire from an unknown killer. Castle wants to solve the case fast because it means Beckett will no longer have to be with the charming entrepreneur.

After tracking a killer to his apartment, Beckett steps on a bomb trigger and must stand in place while the bomb squad finds a way to defuse it. Castle stays with her, and they argue over who liked who first, via flashbacks.

When Homeland Security inexplicably seals the crime scene of a car bombing, Castle and Beckett find themselves with two mysteries on their hands: who murdered the victim, a government whistleblower, and why are federal agents trying to take over the case? The plot thickens when they discover that the victim wasn't killed by a car bomb but by a missile from a military drone.

The team investigates the death of a woman who hacked a law office for a specific file. It seems she thought her best friend was killed, and she was on a lead to that killer. Beckett interviews with the FBI.

Castle and Beckett are engaged. Beckett starts FBI training in Washington D.C. and is assigned to a case. Someone broke into a secured building and may have stolen codes. Castle flies to D.C. and is exposed to a deadly toxin. The code theft was a diversion.

The FBI continues to track leads to the person who stole the deadly chemical. It is a race against time, since they need the antidote for Castle who has been infected with the chemical.

Esposito and Ryan investigate a former TV star's murder, but Beckett and her partner take over the case and do not want them, or Castle, involved.

A woman wakes to find her boyfriend murdered in her apartment. She eludes police and takes hostages and waits for Castle to help her. Castle believes she has been framed, and works with the team to prove her innocence.

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.

The team investigates the ritual murder of a woman. Symbols on the woman's body and the items left in her apartment seem reminiscent of The Da Vinci Code. Alexis and Pi have moved to their own apartment. Castle finds it hard to accept.

Alexis volunteers in a criminal review organization to help prove a man was wrongly accused of murder 15 years ago. With his execution scheduled in three days, Alexis asks her father to bring a new look at the evidence.

A renowned relationship therapist is murdered. The team investigate a couple whose files are missing from the office, and find a perfect, priceless, 100 karat diamond is at the heart of the mystery.

When a woman who looks very similar to Lanie is murdered, the team thinks the killer may be targeting members of the 12th precinct.

A man dies inside a church, protecting a baby. The team has to find the guy's killer and the baby's parents. The man is connected to a crime, but by protecting the baby he does not fit a normal criminal character.

Castle and Beckett must find a serial arsonist as Ryan and Esposito struggle for their life in a building set on fire.

Castle and Beckett have to deal with the sudden appearance of Castle's father while solving the murder of a computer hacker who was working for the covert agent.

When a rising young pop star is found dead in an alley, Castle and Beckett delve into the victim's out-of-control hard-partying lifestyle, but as they dig deeper, a shocking revelation threatens to rock their investigation.

The murder of a PA at a top fashion magazine brings Castle and Beckett face to face with a tangled web of suspicion and corporate politics - and with the magazine's formidable editor, who still remembers Beckett's brief career as a model.

Castle and Beckett investigate the death of a mean high school girl at one of Castle's alma maters. Castle is thrilled when he discovers that it might be the work of a teenage telekinetic.

Castle and Beckett are baffled when a confused woman with an unshakable alibi gives a detailed and convincing confession to a murder. Then a second person walks into the precinct and makes the same confession. And then a third.

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 against some of the most dangerous men in the New York underworld - including a powerful enemy from her past.

Investigating the killing of a Japanese ballerina, Castle and Beckett find a shrine with the murder weapon in an old factory. Then, when the two are separated, Castle is ambushed by a hooded attacker bearing all the hallmarks of a ninja.

Investigating the death of a Wall Street trader leads Castle and Beckett to discover that the victim was an undercover informant for the U.S. Attorney's office.

When construction workers uncover a mobster's body buried in concrete for 35 years, Castle and Beckett must try to talk to a fellow mafioso so stricken with grief that he lives as a recluse in a Seventies time-warp.

A promising professional skateboarder is killed by a motorcyclist, so Castle and Beckett dive into the world of extreme sports to investigate the murder.

A man Beckett has been secretly following is found dead - and then a notorious criminal involved in the first death is killed with Beckett's own gun. Faced with an elaborate frame-up, she has no choice but to run.

The wait is finally over for Castle as the wedding day approaches. Kate discovers that she's still married to her college sweetheart, and visits him to get a divorce. But he has problems of his own, bigger than anyone could imagine.

Beckett is faced with the toughest case of her career after finding Castle's car engulfed in flames.

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.

When a pool shark is murdered by an unseen force, Castle and Beckett uncover evidence that the killer may have paranormal powers. Meanwhile, Castle and Beckett attempt to get their lives back to normal following his disappearance.

Beckett and Castle investigate the shooting of an ice cream vendor and clues lead them to suspect that an unknown second grade child might be able to help them solve the case; Castle goes undercover at a school to try and find the student.

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 realise they are up against a social media sociopath who may strike again.

When Castle gets knocked out while tracking some criminals with Beckett, he wakes up to a world in which he and Kate have never met.

When Castle and Beckett learn that a murder victim may have been poisoned at an Old West-style resort, they visit the resort posing as newlyweds to uncover the truth.

When Castle and Beckett stumble upon an activist as a prime suspect, the NYPD goes on a manhunt, and the consequences could be deadly for one member of the team.

After Castle finds out that his most beloved 1980's movie star has been murdered, he and Beckett receive aid from a group of older action heroes, and investigate the man's heavily guarded past in hopes that it will lead them to his killer.

Castle works for a mafia don to solve the murder of a mob doctor. Esposito has dinner with Lanie and her parents.

Castle becomes a Private Investigator and tries to solve a case before the precinct can.

While Beckett and her team investigate the murder of a young telenovela actress, Castle is hired by the show's star to follow the case from a different angle.

Castle is hired to uncover whether a client's husband is having an affair, but the case takes a shocking turn when Castle witnesses the client's murder - by her husband. But with no proof that the killing took place, Castle and Beckett must investigate to expose the truth.

The serial killer Jerry Tyson, known as 3XK, is back and Castle and Beckett find themselves face-to-face with him at the precinct. Can they put him away for good?

The NYPD searches for Beckett while 3XK calmly plays with them.

When an astronaut in a Mars simulation is killed, Castle and Beckett don spacesuits and enter the simulation to investigate. Much to their surprise, it seems no one inside and no one outside could have committed the murder.

A Hong Kong Detective works with Beckett and Castle on the murder of an ex-con turned tow truck driver.

Detective Ryan ends up in the middle of an assassination plot when he is on the security detail of a charismatic congressman; Castle and Beckett help Ryan investigate.

Beckett and Castle are faced with a large list of possible suspects when a personal injury attorney known as Richie "The Pitbull" Falco is murdered; a shocking secret deepens the mystery surrounding Richie's death.

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

Beckett must help Castle and Alexis from the ground when the Air Marshal on their flight is found murdered in mid-air.

The creator of a sketch-comedy show is murdered, and the investigation yields a surprising secret.

A death occurs in the woods and Castle becomes obsessed with the case because it reminds him of a pivotal event in his childhood. Beckett reaches a turning point in her life.

Investigating the death of a Wall Street trader leads Castle and Beckett to discover that the victim was an undercover informant for the U.S. Attorney's office.

Hannah Green, star of a reality show, is found dead at a bus stop with a knife in her back. She has bruises from being held captive for the day she went missing from the studio. The team unravels complex rivalries for parts, infidelity and spin-offs that affect both a clothing line and Margo's son Stone Gower's series project with co-star Collette's daughter, Ashley. Castle and Becket fear the captain will discover their affair after he accidentally drops Beckett's Valentine present in the wrong coat.

Wendy Dupree, murdered in a cheap motel, wrote a clue in her blood. When Castle realizes it's no word but a number, it leads, in combination with her phone records, to a storage compartment, about to be auctioned, rented by her brother Wendell, an ex-con, who died in a suspicious accident a few months earlier. He was employed as driver by socialite Anjelica Henley, who recently reported a super-valuable diamond, stolen in a robbery, focus of further criminal intrigues. The earlier past provides the crucial clues, while Castle and his mother worry about Alexis's impending moving out to a dorm, albeit in New York.

After tracking a killer to his apartment, Beckett steps on a bomb trigger and must stand in place while the bomb squad finds a way to defuse it. Castle stays with her, and they argue over who liked who first, via flashbacks.

When Castle and Beckett learn that a murder victim may have been poisoned at an Old West-style resort, they visit the resort posing as newlyweds to uncover the truth.

A woman wakes to find her boyfriend murdered in her apartment. She eludes police and takes hostages and waits for Castle to help her. Castle believes she has been framed, and works with the team to prove her innocence.

The NYPD searches for Beckett while 3XK calmly plays with them.

A man Beckett has been secretly following is found dead - and then a notorious criminal involved in the first death is killed with Beckett's own gun. Faced with an elaborate frame-up, she has no choice but to run.

When Beckett and Castle pick up a witness to a murder, hired killers attack, and they lose their cell phones and Beckett's gun. They run for protection while Esposito and Ryan try to find them.

A man dressed as Santa falls from the sky while Castle and Beckett prepare for their first Christmas as a couple.