The Machine gives Finch and Reese the number of a brilliant surgeon, but they soon discover that a resourceful third party has raised the stakes for this POI, forcing them to turn to an unlikely source for help.
Terrifying hallucinations leave Elena shaken and confused, causing her to make a dangerous mistake. After giving Stefan some very disturbing news about Elena, Klaus takes matters into his own hands. Professor Shane reveals a story of ancient witchcraft to Damon and Bonnie. With help from Klaus and Stefan, Jeremy begins a new chapter in his life. Finally, Elena makes a painful personal confession to Stefan, and Matt gives Damon startling new information about Professor Shane.
Sam and Marcus look for the traitor who stole the nuclear launch key; when Prosser disobeys orders, he starts a conflict he can't control; Grace and James try to defuse a dangerous situation.
Sherlock assists with a double homicide that has the same M.O. as a series of murders that took place 13 years ago. Meanwhile, after being frozen out by Sherlock, Watson visits his old rehab center in order to learn more about the mysterious man in her care.
Michael is accused of a crime at a local hotel. Elsewhere, Olivia questions Sam in an attempt to get to Michael.
October 16, 1864. Corcoran and O’Brien investigate a peculiar double murder. Five Points gathers to watch the exhibition fight between Jasper Longfield and “Irish” Jake McGinnis. Rebellious Annie continues to terrorize an impatient Elizabeth.
The women of the office try to teach Dwight how to interact with female clients; Angela suspects the senator of cheating; Toby convinces some of the guys to grow mustaches.
Leslie gets upset when April tries to get Lot 48 made into a dog park. Meanwhile, Tom enlists Ben’s help as he tries to launch his new business venture, and Andy hones his crime scene investigation skills.
Mac, Charlie and Dee struggle with their faith as Charlie's mom fights cancer. Meanwhile, Frank loses his memory amidst a search for buried treasure.
Justin, Olive, and Squidgy make an important delivery across the Northwest Passage thanks to a helpful narwhal.
Rachel and Kurt pay a visit to Lima as the glee club launches its production of "Grease". Meanwhile, Cassandra July returns to shake things up in Rachel's life, and Santana comes back to lend a helping hand.
Tom's hot temper lands her in a duel with the world's number one fencing champion, while Leonardo begins work on building his superweapon.
After their flight is cancelled, Chris and Reagan are forced stay home for Thanksgiving.
After she's seemingly stood up by Vincent, Cat wonders if it's because he saw her kissing Evan at her birthday. Actually, Vincent mysteriously blacked out on his way to meet Cat, and is now searching for answers. Cat's case pulls her into the sophisticated world of the SoHo art scene. When Vincent finds Cat all dressed up to go to a gallery opening -- with Evan -- he has to admit that his feelings for her are growing deeper. All the while Evan makes his affections for Cat known, leaving Cat torn between the two very different suitors.
Alan feels reluctant to make a commitment to Lyndsey, but an unexpected source inspires him; Walden enjoys being the boy-toy of a wealthy older woman.
When Claire takes Manny and Luke along to Alex's academic decathlon for the weekend, Phil attempts to throw together a boys' night at the house. Cam and Mitch arrange for quite the surprise baby gift for Jay and Gloria.
Sister Jude employs a renowned Nazi hunter to gather evidence against Arden; Kit makes a surprising confession; Bloody Face is unmasked.
Sam and Dean are stunned when Castiel suddenly appears back on Earth with no memory of how he escaped from Purgatory. Meanwhile, Mrs. Tran enlists a witch to concoct a demon bomb.
The teens of Berk find a mysterious girl named Heather on Thor's Beach. While Hiccup and the other teens openly welcome the newcomer, Astrid's jealousy turns to suspicion when she notices Heather is taking an unusual interest in the Book of Dragons.
Facing suspension, Dawson gets a hand from the same girl she saved through the procedures that landed her in front of the disciplinary board. Lieutenant Casey finds his fuse shortening as Detective Voight stops at nothing to get him to retract his statement. However, when Casey lays his life on the line during an apartment fire, he may have unknowingly caught the break he was needing.