After the fight between Jake and Sam, Dean has to make the ultimate sacrifice for his brother. Meanwhile the Yellow-Eyed Demon has his new servant and plans to unleash the hordes of Hell.
After Pam's outburst at Beach Day, she and Jim had a talk and realized how much they both missed their friendship. Pam never regretted her speech she gave to Jim in front of the rest of the staff; in fact, she was happy that it only took her three years to summon the courage to say what was on her mind.
As the CSI's continue their search for and discover the identity of the "Miniature Killer", Grissom and Sara's relationship gets exposed to the rest of the team as she goes missing during the investigation. The "Miniature Killer" is finally captured, but not before a member of CSI becomes the killer's final victim.
Kim moves in with J.D. in order to raise their child together. J.D. learns from Turk and Dr. Cox that fatherhood changes the way of how to see things. Carla complains to Elliot about her being a control freak when they prepare the bachelorette party.
In the season finale, J.D. and Elliot start thinking about their future and if they both made a mistake in not being with each other. The Janitor activates the "Brain Trust" to come up with the perfect wedding gift for Elliot.
Betty and Henry's romance heats up. Meanwhile, Wilhelmina makes great strides in her ambitious power play, as Daniel descends further in a downward spiral. The Suarez family trip to Mexico takes a dangerous turn, with old ghosts creating new problems. Explosive secrets will be revealed, and everything will be tied together by a beloved Broadway musical.
Season Finale: Luka postpones his honeymoon, leaving Abby, Joe and the ER behind to begin a different journey. Meanwhile, it's Moretti's first day as Chief of Emergency Medicine, and everyone feels the effects of his style, especially Pratt and Morris. Neela learns of Ray's fate, then joins an anti-war rally and finds herself in a dangerous situation. Gates faces a crisis on the home front.
After hearing about a powerful Buizel thwarting trainers' attempts at capture, Ash, Dawn and Brock decides to do a round of fishing in hopes of finding it. During their fishing round, Ash and friends are joined by Dawn's contest rival, Zoey.
Michael, Jim and Karen interview for a job at corporate; Michael appoints Dwight as regional manager.
The mountain climbers lie about the axe in their friend's head, telling Derek that it accidentally got there. During surgery, he and George discover that it was deliberately put there, and one of the climbers admit that he was trying to "put him out of his misery". Adele is saved after Richard finds her lying in the bathroom and is stabilized, but soon suffers a miscarriage. Richard learns Adele was actually pregnant with his son, not someone she had one night stand with. Bailey is disappointed to see that Callie is the new Chief Resident and begins to question her abilities as a surgeon. Richard chooses Derek as Chief of Surgery, but he refuses, telling him that he isn't done doing what he does best. Cristina and Burke's wedding day arrives, but Cristina won't stay out of the hospital. However, Cristina's nervousness results in Burke's realizing that he does not love the real Cristina and leaves her. Meredith and Derek are uncertain about their future and despite Derek admitting that she is the love of his life, they call their relationship over.
Having just picked up 18 corpses with no visible cause of death from a cargo ship, the Mys Venezia, the whole gang is aboard a 737, flying into a storm. Nigel thinks it's aliens or pirates that are the cause of the deaths, but all speculation ends when co-pilot Dave Rosso tells everyone to buckle up, because they have to fly into the storm. When the engines blow out, the hatch blows off, and the plane starts to dive, Dave tells everyone to brace for the inevitable crash.
Cheryl throws Jim an unwanted surprise party for his 50th birthday, which Jim then sabotages, and then later reveals the real reason why he won't celebrate his birthday.
Dr. Good helps Ralph Macchio unleash is inner child; and Liz Phair opens up about her love life.
While Jack devises a plan to do away with "The Others" once and for all, Sayid uncovers a flaw in "The Others'" system that could lead to everyone's rescue. But it requires Charlie to take on a dangerous task that may make Desmond's premonition come true. A Charlie-centric episode.
Brooke and Peyton finally rekindle their friendship, Nathan's past mistakes continue to haunt him and Haley, and Lucas hears a shocking confession from the witness to Keith's murder.
When the prolific serial killer Frank returns and murders Gideon's girlfriend, Gideon takes off to find him without telling the team where he is going. The BAU must then profile Gideon as well as Frank to find both of them.
After Flack makes an enormous drug bust, and locks it up at CSI, the drug lords infiltrate the building at gunpoint to get them back. Now the team must resolve the hostage situations, all the while with Mac, Stella, and Hawkes trapped inside.
When Angela draws the face of an old woman to go with the decomposed skeleton of someone much younger, they soon learn the victim had Progeria, an aging disease. Booth and Brennan investigate to discover who would want to kill such a fragile person. Meanwhile, Hodgins and Angela's walk down the aisle doesn't go as planned.
P.D. McCall's betrayal has devastating results for everyone in Allison's life, and Walter Paxton brokers a deal with the D.A.'s office.
In the third season finale, Allison's life, along with the lives of her family, is uprooted as her psychic abilities are revealed to the public. Allison must now find a way to catch the "recapitator" serial killer on her own, as she can no longer turn to Devalos or Scanlon for help.