Detective Slaughter (guest star Adam Baldwin) returns to enlist Castle’s help in solving a high-stakes robbery case.
"Death Gone Crazy" - 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.
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 Castle and Martha are taken hostage by a crew of bank robbers dressed in hospital scrubs and using classic television doctor names (Trapper John M.D., Dr. Huxtable, Dr. Quinn Medicine Woman and Dr. Doogie Howser), 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 (guest star Dean Norris, "Breaking Bad") watching her every move. Castle becomes the de facto leader of the hostages, which includes Barry Livingston ("My Three Sons"), 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?
"Scared to Death" -- When a young woman appears to have literally been scared to death three days after watching a "haunted" DVD, Castle and Beckett delve into one of their creepiest cases yet. To make matters worse, Castle becomes convinced that he too is marked for death when he accidentally watches the cursed video. Master of horror Wes Craven makes a special quest appearance.
"Headhunters" - 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.
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. Krista Allen and Ted McGinley guest star.
"Hunt" -- 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.
"The Wild Rover" - 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 (guest star Cara Buono, "Mad Men"). 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 part two of last week’s Season 8 premiere, 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.