Beckett hasn't heard from Castle since he left for the Hamptons months ago to finish writing his second Nikki Heat novel, "Naked Heat." The most Beckett, Ryan and Esposito have seen of Castle is a bookstore standee of him advertising an upcoming book signing. So when Beckett and her team burst into a shadowy apartment on the trail of a murderer, the last thing they expect to see is the real-life Castle standing over a dead woman's body holding a gun. As Castle protests his innocence, Beckett has no choice but to arrest him on suspicion of murder.

When a famous psychic is murdered, Beckett and Castle search for her killer while also carrying on a spirited debate on the existence of extrasensory abilities. Evidence mounts on both sides, especially when a letter arrives from the victim, penned the day she was killed and predicting her own death -- or was it written by a clever killer, hoping to throw off the investigation?

When a coded document hidden by a murdered bail bondsman gets Castle's imagination running wild, Beckett must steer the case back to the violent felons who populated their victim's world - only to discover that maybe Castle's crazy theories aren't so crazy after all. Complicating matters is the surprise arrival of Beckett's ex-partner (now a bounty hunter). As the two reunite over a history that Castle has no part of, Castle is forced to watch the relationship take a turn towards the romantic.

Castle and Beckett look into the murder of a young mathematician gunned down with a 200-year-old bullet, sparking some wild theories by Castle about a time-travelling killer. When their investigation uncovers a tricked-out DeLorean and a suspect in Victorian clothing, is it possible Castle's crazy idea has some validity? This winding tale twists through the towers of Wall Street and into the world of a secret steampunk society that embraces the romance and simplicity of the past, while coupling it with the hope and promise of the future.

Mysteries abound when pallbearers at a funeral lose control of a surprisingly heavy casket only to have a second unknown woman tumble out along with the original deceased. When Castle and Beckett learn that the victim was a doctor at County Hospital, their investigation takes them into the world of amorous, bed-hopping physicians. Did jealousy turn to murder, or did the doctor's mysterious work outside the hospital lead to her demise? Meanwhile, Castle's relationship with Gina is challenged when she tries to bond with Alexis.

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.

Responding to an "Officer Down" emergency call, Castle and Beckett's latest case takes a shocking turn when it's revealed that the victim isn't a cop but a male stripper dressed up as one. The murder leads them into the world of male strip clubs, the hardships of struggling actors, and the price that people pay in pursuit of fame. Did our victim's dreams of stardom get him killed, or was there something more nefarious afoot?

While investigating the murder of a NYC subway worker found shot to death in Central Park, Castle and Beckett unexpectedly uncover the shocking and violent abduction of a young boy. Working against the clock, the team must unravel the motives behind the high stakes kidnapping, not just to bring a murderer to justice, but to save the innocent lives that hang in the balance.

Astrophysicist Marie Subbarao (35)'s corpse is found, with all symptoms of fatal explosive decompression. Her ex Ted Carter, a colleague at the institute, has an alibi. An SF author friend also points to Castle's remark that everything seems to point to aliens. However the team's digging leads to FBI agent Westfield, whose agency goes to extraordinary lengths to stop their investigation, yet fails to keep from them Chinese Ung Kyu's involvement.

When the body of a dockworker turned bar owner is found floating in the East River, Castle and Beckett's investigation takes them into the forgotten tunnels and passageways of turn-of-the-century New York, where they uncover a secret that's been buried since the days of Prohibition. The story celebrates New York bar culture, setting Castle on a quest to preserve history by buying a bar of his very own.

Castle's novel "Heat Wave" is being turned into a movie, and the Hollywood hottie cast as the movie's lead, Natalie Rhodes, shows up at Beckett's invitation to better understand the character she's going to play. As our threesome investigates the murder of a high-class matchmaker, Natalie goes to extremes in the name of "character research," transforming herself into the spitting image of Beckett -- much to Castle's delight and Beckett's dismay.

When the owner of historic Drake's Magic Shop in New York is found drowned in Houdini's famous water torture tank, Castle and Beckett must delve into the world of magic, magicians and their secrets to find his killer. As part of their investigation, Castle & Beckett meet master magician Tobias Strange. Meanwhile, the magicians aren't the only ones keeping secrets, as a new romantic relationship is revealed for Esposito and Lanie.

The detective on Beckett's mother's homicide case is killed after telling her he has information.

Lottery-multimillionaire Jay Hixton is shot in the heart at home around midnight. He was apparently forced to open his safe. It contained a gun even butler Reginald Easley didn't know about, which was laid besides him, and a bag, which was taken, containing $100,000 cash and a blue dye bomb, which exploded in a maintenance worker's face. Various suspects arise from Hixton's bizarre generosity, his own murky past and his family, an ex and junkie daughter, and even his winning lottery ticket a year ago.

Castle and Beckett find themselves on opposite sides of the case when Castle's old school friend emerges as the prime suspect in his own wife's murder. As they work to solve the crime, Castle comes to realize that one of two terrible things must be true... Either Detective Beckett is about to arrest an innocent man for murder, or his old friend is a cold-blooded killer.

Recently US-nationalized Syrian cab driver Amir Alhabi, who runs his own company with cousin Fariq Yusef, is shot in his cab after a 45 tour back to the start point with consulate 'security attaché' (spy) Fariq Yusef. Homeland Security Agent Mark Fallon takes charge after his keys lead to a storage unit with cobalt radiation feared to stem from a nuclear weapon. Castle is officially discarded but keeps in the loop, tracing a payment to Amir, which he believes a fake as cover-up, shifting focus to employed cab driver Kevin McCann.

Clever Castle's ideas get him and Becket to find the dirty bomb, but locked in a refrigeration car incommunicado. Luckily Ryan and Esposito ignore priority orders to have them found, and hence the bomb's trail. Agent Mark Fallon lifts their official ban from the case and follows Castle's next ideas about identity, widows and an Afghan-military connection. Add Fallon's interrogation zeal and they're just in time to discover the dark motive and find the bomb, but armed and about to explode and wipe out Manhattan.

Martha's connections in soap operas prove dangerous as well as practical and sexy when the chief script writer on "Temptation Lane," which once made Martha's career, is axe-murdered. After wading through theories based on actor career opportunism and private infidelity plus some far-fetched ones, Castle sets a scripted trap.

Juror #7 Joe McKusick, who runs a halfway house, drops dead cyanide-poisoned during Otis Williams's high-profile trial for the murder of heiress Lyla Addison, which is thus declared a mistrial. Juror #4 Tony Mueller runs, possibly bribed, but claims he believed Otis's cousin Wardell, who approached him implying a set-up, poisoned Joe, which fits security footage, and he'd be next. Wardell claims to be framed too. The cyanide came not from the court house vending machine coffee but was released from a capsule. The plot thickens further.

Castle knows of four pizzerias named "Nick," with various combinations of the predicates terrific and/or authentic. But their owners, bitter rivals, continually sabotage each other with frat pranks. Then a corpse is found in the pizzeria oven, crisped, but killed by previous stabbing. The owner accuses his rivals, but no one is innocent and everyone has a dirty secret. And the victim, a former war correspondent who lost his edge after his daughter died in a car accident, was reporting on them about their "pizza wars." However, he'd also stumbled across the identity of...

College swimming team champion Zack Lindsey, self-made on a partial scholarship, is murdered during a nightly training session and dumped in the pool. Beckett and Castle wade through Zach's, his teammates', his coach's and even retired predecessor Rob 'Rocket' Tredwyck dodgy connections, motives and alibis, involving car theft and doping. Meanwhile, Castle soon regrets bringing along his writing protégé Alex Conrad, whom Beckett surprisingly welcomes as eagerly as his crime authors' poker club proves jealously aloof.

Mike Royce, Becket's former police mentor, who lost his bounty-hunter license when she arrested him, is murdered while visiting New York, possibly by a fellow passenger from L.A. The captain takes her off the case but she uses extant leave. Castle comes along, having to visit his book's movie set anyway. Informally backed up by Ryan and Esposito, hey soon find Royce must have been after the manufacturer of the dissolving type of bullet he was killed with. The trail of arms-dealings and new crimes leads back to New York, fortunately as LAPD detective Kyle Seeger.

Mysterious murder occurs during a beauty pageant and the suspects are plentiful.

Cop killer Hal Lockwood, whom Becket visited unsuccessfully in jail for months hoping for a lead in her mother Johanna's closed murder case, is released by a faked order into the general population, where he slices fellow rogue cop Gary McCallister's throat, then is helped by fake cops to escape. Becket, his likely next target, receives warnings from her father, Montgomery and Castle. Much helped by Ryan and Esposito, the duo work out there must be a police accomplice and/or mastermind controlling Chuck Ryker, the debt-ridden corrupt jailer who was found murdered.