Owen and the team race to deal with a runaway bull at a used car lot and an apparent electrocution at the hands of an LA transplant. Meanwhile, Owen is determined to prove he is physically fit for the job while undergoing chemo and Michelle gets the strongest lead yet on her missing sister.

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.

Threatened with expulsion, Yumyulack and Jesse continue to attend their empty high school after the school year ends. Unaware of the summer break, they believe they are being tested, and attempt to teach each other. They realize their mistake and wreak havoc on the school, and are bribed with straight As after discovering Principal Cooke and Mrs. Frankie having sex in the cafeteria. Korvo and Terry enroll in a junior college, but Terry shoots Korvo with a raygun that makes him dumber. Korvo joins Terry's hard-partying college experience, but accidentally causes the "ice lava" that powers their spaceship to flood the city, freezing everyone in its path.

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.

The BAU heads to Wichita in search of an UnSub abducting children while their parents sleep. Also, Morgan tries to find who was responsible for his attack.

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 an UnSub targets the BAU, and the team goes into action to find out who is responsible.

Castle and Beckett take on a murder at a sci-fi convention.

The team gets closer to uncovering the identity of The Disciple.

Emergencies include a ride-share trip gone awry, a farming accident and a memorial service that may turn into another funeral. Owen unexpectedly bonds with the former Captain of the 126, while Marjan and the crew help Mateo try to pass his written exams.

The team investigates the body of a private investigator who was found frozen in ice, after being dumped in the Potomac. The victim, a man with many enemies, was a "fixer" who made sure his cllients' problems got "resolved." Meanwhile, Aubrey is shocked to find information tied to his father's whereabouts, Angela and Hodgins continue to work on their rocky relationship, Brennan and Booth get Christine's first report card and criminal behaviorist Karen Delfs (guest star Sara Rue) asks Aubrey out on a date.

The BAU heads to Wichita in search of an UnSub abducting children while their parents sleep. Also, Morgan tries to find who was responsible for his attack.

When an UnSub targets the BAU, and the team goes into action to find out who is responsible.

Harrow resolves to believe that Chester really is dead, and takes a case in North Queensland, while Simon launches his own investigation into Chester.

The team gets closer to uncovering the identity of The Disciple.

Beckett and Castle are followed by a documentary crew as they investigate the murder of a rock star.

The team investigates the death of the leader of the Lynwood University male acapella singing group, "The Whippersnaps," whose body was found in the school rat lab. The victim recently kicked out Ian Jansen, one of the group's best singers (guest star Jordan Fisher), sending Booth and Aubrey to question Ian and other current members of the male group (including guest stars Mitch Grassi and Scott Hoying) and some stars of the competing female acapella group (including guest star Kristin Maldonado) to get a handle on the group dynamics and what could have led to the murder of one of their own. Meanwhile, surprising information about Aubrey's own college experience is brought to light, Hodgins applies for an experimental nerve regeneration study, Booth tries to plan a summer trip with Parker (guest star Gavin MacIntosh) and a new intern joins the Jeffersonian lab (guest star B.K. Cannon).

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.

Owen and the team race to deal with a runaway bull at a used car lot and an apparent electrocution at the hands of an LA transplant. Meanwhile, Owen is determined to prove he is physically fit for the job while undergoing chemo and Michelle gets the strongest lead yet on her missing sister.

When former BAU team member and current Interpol Agent Emily Prentiss tracks an international serial killer, she enlists the help of her friends at the BAU after she is convinced the UnSub's next victim is on American soil. Also, the BAU deals with Morgan's departure from the team.

The BAU searches for an UnSub who is purposely disfiguring victims. Also, Rossi has an awkward reunion with his ex-wife, Hayden Montgomery, who kept his daughter, Joy, a secret from him for nearly 30 years.

Coping with a death that strikes close to home by focusing on work, Harrow is stunned to discover a connection between this death and another deceased man on his autopsy table.

R.J. unravels the truth about a Little League coach whose family is being mysteriously targeted; R.J.'s parole officer worries that he is pushing the boundaries of his conditional release.

The team gets closer to uncovering the identity of The Disciple.

Beckett and Castle are followed by a documentary crew as they investigate the murder of a rock star.

Coping with a death that strikes close to home by focusing on work, Harrow is stunned to discover a connection between this death and another deceased man on his autopsy table.

A drunk college student discovers the dead body of a Secret Service agent just before a presidential visit to the area. Booth is ready to hit the ground running and turns to Secret Service agent and former colleague Brandt Walker for information, but is surprised to learn the Secret Service has reservations about Booth's involvement in the case. The team uncovers some shocking evidence that heightens the seriousness of the case, causing Booth to step up for his country. Meanwhile, Brennan is out sick with the flu and former intern Dr. Colin Fisher returns to the Jeffersonian to run lead on the case, but Brennan refuses to be kept out of the loop. Also, Hodgins takes his life into his own hands and turns a corner after a potentially dangerous experiment.

The BAU enters into a dangerous game of cat-and-mouse with a convicted serial killer after guards at a Virginia prison intercept a package with evidence relating to the kidnapping of two boys several years ago. The team believes the notorious killer may have information on the boys' whereabouts.

Owen, Michelle and the 126 crew race to a rattlesnake infestation at a young family's home, and attempt to rescue a man with dementia from a dangerous scene that he created. Meanwhile, Owen adopts a firehouse dog with cancer and Michelle finally learns the truth behind her sister's disappearance. Also, a tragic accident shakes the team to its core.

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.

Hotch is apprehended for suspected conspiracy and the BAU suspects a larger plot may be brewing.