After four seasons of "will they" or "won't they," Richard Castle and Kate Beckett finally gave in to their feelings for each other in the much anticipated Season 4 finale. Season 5 picks up on the proverbial morning after, with Castle and Beckett facing new questions -- Was this a one-time fling, or are they now a couple? But before they find the answers, they must take on the forces responsible for Beckett's mother's murder that now threaten Kate Beckett's life.

Beckett is finally back to the NYPD after serving her suspension, and concerned about keeping her relationship with Castle a secret in the workplace. The team is baffled with the murder of local celebrity WHNY's weather girl Mandy Michaels, because there is no apparent motive for the murder. As the investigation progresses, Castle takes playing single in public in order to advert suspicion on the relationship a little bit too much to heart as he goes on a date with Kristina Kotera, WHNY's sexy celebrity interviewer, the woman who doesn't take no for an answer.

When a young woman is mysteriously murdered, Beckett and Castle discover her death may be linked to a repossessed storage unit up for auction. Was the unit connected to her death? Was something inside it worth killing for? The investigation leads Castle and Beckett to colorful “Storage Wars”-like treasure seekers and Manhattan socialites as they uncover the shocking 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.

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.

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.

When the lead guitarist of a rock band is murdered, the documentary crew that were following the band turn their cameras on Castle, Beckett and the team as they try to solve the case. The result is a documentary style episode of Castle, which offers us a unique glimpse at our characters as they navigate a world that goes far beyond the rock & roll stage.

In the aftermath of a disastrous "Meet the Parents" dinner, a bickering Castle and Beckett are sent to retrieve the only witness to a murder. But when they get ambushed, they're forced to take the witness on the run. Stranded in the middle of the night in a bad part of town, with no phone, badge or gun, Castle and Beckett must find a way to protect him from a team of mobsters who want him silenced — that is, if they don't kill each other first.

When a bearded, rotund man in a red Santa suit with an ID reading Kris Kringle falls from the sky in Central Park, Castle and Beckett are on the hunt to find the person who killed Santa. But everything isn't holiday cheer, as they discover St. Nick may have been more naughty than nice. Meanwhile, Castle and Beckett prepare for their first Christmas together.

When a powerful divorce attorney who only represented women is murdered, Castle and Beckett are confronted with a plethora of angry ex-husbands, any one of whom could be the murderer. Meanwhile, Castle's ex-wife, Meredith, moves into the loft to take care of Alexis while she recovers from Mono, and to make matters worse, Beckett is also forced to move in while her apartment is being fumigated, causing tension, humor and more than a little awkwardness.

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 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 in the episode, Alexis starts a video blog, but Castle is not happy that personal and intimate details about her life are being made public.

While investigating the murder of a young woman, Castle and Beckett find evidence that links her death with Senator William H. Bracken (guest star Jack Coleman returns), the man responsible for Beckett's mother's murder. Determined to finally bring Bracken to justice, Beckett soon realizes that things are far more complicated than they seem.

Castle and Beckett get an up-close-and-personal view of a Real Housewives-esque reality TV series, The Wives of Wall Street, when they investigate the murder of the show's rising young star. Meanwhile, Castle's attempt to give Beckett a Valentine's Day gift goes horribly wrong.

While investigating a murder, Castle and Beckett find a link to a kidnapping plot. FBI Agent Harris is called in to help find the kidnappers.

When Castle takes matters into his own hands, after the FBI fail to get Alexis back, he discovers that the kidnapping may be part of something more ominous.

A "haunted" video seems to have scared a young woman to death and now Castle is convinced he's next after inadvertently watching the cursed video.

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 (Cara Buono). 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.

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.

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.

When Beckett is assigned to protect Erik Vaughn, a charming billionaire entrepreneur whose life is in danger, she's forced to reflect on her relationship with Castle which has begun to plateau. Meanwhile, consumed with jealousy, Castle goes to extraordinary lengths to solve the case and separate the two of them.

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 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.

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.