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.

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.

With tensions rising between Castle and Beckett, Castle finds himself a new partner -- Detective Ethan Slaughter, 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.

Devilishly handsome detective from Scotland Yard, Simon Hunt, teams up with Castle & Beckett to find the person responsible for the murder of his friend's daughter. Also, Charles Shaughnessy plays Nigel Winthrop, the Deputy General at the British Consulate whom Castle & Beckett suspect 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.

When a bomb explodes at a protest rally killing five people, Castle & 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 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.

When a woman dressed as Red Riding Hood is found dead in the woods with claw marks covering her body, and soon after a murdered Snow White is discovered with a poison apple in her hand, Castle & Beckett find themselves on a Grimm hunt to catch a fairytale killer before he kills again. But nothing is as it seems in a case filled with deceit, betrayal, secrets and murder.

In the explosive conclusion of a two-part story arc that began last week with "Pandora," 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.

In the first episode of a two-part "Castle" event, 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. Josh Stamberg, also guest stars as Martin Danberg, an intelligence officer.

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.

When a famous dog trainer is killed, the investigation keeps coming back to charismatic reality TV star Kay Cappuccio. Kay, a favorite of tabloids and gossip websites the world over, has achieved stardom without possessing any discernible skill or talent. But there seems to be more to her story than she is letting on -- does that include murder?

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

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 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.

Sniper on a killing spree is terrorizing New York City. With the clock ticking down to the next murder and nothing to go on except a killer with no apparent motive but to instill terror, this could prove the team's toughest case yet. The hunt is made even more complicated when Beckett begins to experience increasingly strong moments of PTSD - moments she tries hard to hide from Castle and the detectives.

During the investigation of the murder of an Atlantic City casino owner at an abandoned warehouse, strong leads emerge for the team in both New York and Atlantic City. As Beckett and Capt. Gates work the New York leads together, Castle naturally chooses to join the detectives for the road trip to "America's Playground," hoping to help solve the case while throwing an impromptu bachelor party for Ryan. Richard Burgi guest stars as Charlie Turner, the slick business partner of the victim.

When Castle and Martha are taken hostage by a crew of bank robbers dressed in hospital scrubs and using classic television doctor names, Beckett finds herself on the outside, desperately trying to rescue them -- which proves to be even more difficult with a by-the-book hostage negotiator watching her every move. Castle becomes the de facto leader of the hostages, which includes Barry Livingston, and discovers that the robbery is actually a skillfully orchestrated distraction for an even more sinister plan. But with Castle stuck on the inside and Beckett on the outside, will either be able to foil the bank robbers' plans before it is too late?

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

Castle & Beckett work a murder case around the theft of a valuable sculpture. Kristin Lehman guest stars as Serena Kaye, a smart, sexy insurance investigator, who joins Castle & Beckett in the investigation, but she also has her eyes set on Castle, all the while hiding a very important secret from the team. Jessica Tuck also guest stars as Joy McHugh, a wealthy museum benefactor who becomes a suspect in the murder investigation.

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.

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 (guest star William Atherton), and a sleazy porn mogul who invested in a modern-day "fountain of youth." Meanwhile, Alexis finds out whether she got into Stanford.

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?.

In a riveting opening that picks up just moments after last season's climactic finale, 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.