The mysterious death of a hotel maid draws Harrow into a dark world of espionage and assassination, while Nichols edges closer to catching Harrow's wayward son James.

After two men die in a duel, Harrow uncovers a web of Machiavellian intrigue within a suburban historical society. Meanwhile, the return of Tanya forces Harrow to reassess the last twenty years of his life.

London, four months after the attack. The survivors organize the Resistance. Bill continues his research on aliens and understands that their DNA is human but that their organs are degenerating. In France, a severely wounded dissident alien reaches the Observatory

At the Observatory, Mokrani and Catherine clash over the fate to be reserved for Micah, whom Catherine considers to be a major source of information. Micah reveals to Catherine that she has to find Bill Ward. The latter, for his part, tries to find out more about Emily, still assailed by visions of Adina, the leader of the aliens urging him to kill Bill.

A dry thunderstorm rolls over LA, bringing in a series of lightning strike emergencies for the 118 and leaves a first responder’s life hanging in the balance. Athena and May go undercover at the rehab facility to help Bobby with his investigation into his sponsor’s mysterious death. Maddie dreads her parents visit to her and Chimney’s new and unfinished house, while Chimney get a surprise of his own from a visiting Albert.

With Beckett still in D.C., Castle and the boys investigate the murder of former child star Charlie Reynolds, who rose to fame playing the lovable nerd on an early 90s High School sitcom.

A desperate young murder suspect, Emma Briggs, takes hostages at gunpoint then mysteriously insists that she will only negotiate with one person: Richard Castle.

Castle and Beckett investigate the bizarre murder of a young woman who was found ritually posed. When the team finds a collection of strange symbols in her apartment, Castle becomes convinced they’ve stumbled onto a 'Da Vinci Code' style conspiracy.

Castle and Beckett work the murder case of a famed relationship therapist. At first it appears that client secrets may have been the motivating factor, but then a rare valuable object is discovered in the victim's possession.

When Reid fears his mother has been abducted, he asks the BAU to investigate while he's stuck in prison.

Agent Matt Simmons joins the BAU team in a race to take down Mr. Scratch and save one of their own in the process.

Last season ended with Beckett wrestling over whether to take a high-profile job in DC - a dilemma made more complicated when Castle proposed to her. Now Castle and Beckett will deal with the consequences of their decisions.

With Beckett still in D.C., Castle and the boys investigate the murder of former child star Charlie Reynolds, who rose to fame playing the lovable nerd on an early 90s High School sitcom.

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.

An unidentifiable body is discovered in the shower of an upscale home belonging to a young female socialite.

The city anxiously anticipates the arrival of Heather Taffet, known as 'The Gravedigger', for her final appeal after being sentenced to death for a kidnap-murder and a series of similar crimes. When she is shot by a sniper, the Jeffersonian team investigates.

A body disguised as a scarecrow is found with a bullet wound in a remote cornfield, and the team is forced to work against the clock to avoid a storm and potential complications that would affect the evidence.

Comes to the team with a lead that might help catch Mr. Scratch, the elusive fugitive that has been tormenting the team all season.

The BAU investigates three similar crimes in which victims' remains are discovered in old suitcases.

While pressure mounts on Harrow to stop defending his son James, two baffling deaths demand all his wit and courage to solve - before another life is lost.

The mysterious death of a hotel maid draws Harrow into a dark world of espionage and assassination, while Nichols edges closer to catching Harrow's wayward son James.

R.J. takes on a strange case following a grocery store robbery gone wrong; Emi's loyalty is tested when her father's misdeeds come to light.

When Reid and Garcia are abducted by Benjamin Merva, it's up to the rest of the team to find them. The BAU finds surprising clues in their own history to solve why the two heroes have been targeted by a mass murderer. It's a race to save them before a "Believers" prophecy is fulfilled.

A dry thunderstorm rolls over LA, bringing in a series of lightning strike emergencies for the 118 and leaves a first responder’s life hanging in the balance. Athena and May go undercover at the rehab facility to help Bobby with his investigation into his sponsor’s mysterious death. Maddie dreads her parents visit to her and Chimney’s new and unfinished house, while Chimney get a surprise of his own from a visiting Albert.

When Homeland Security inexplicably seals the crime scene of a car bombing, Castle and Beckett find themselves with two mysteries on their hands.

A BMX rider's remains are discovered on the roof of a warehouse after a failed bike stunt. Sweets turns to Booth for advice about his relationship with Daisy and Booth makes a decision about his relationship with Hannah.

When successful businessmen in Detroit are targeted by an anger-driven power-assertive Unsub, the BAU is called in to investigate.

As Buck’s life hangs in the balance, he dreams of a world where he never became a firefighter, for better and worse.