Klaus takes Stefan to Chicago, where he wants to resuscitate his sister Rebekah, who might hold the key to breaking the curse. Gradually, Stefan is reminded of his Prohibition period affair with her while still bloodthirsty himself, and its tragic end. Tyler is rightly worried, turning for an ally to her mother sheriff Forbes, about the whereabouts of Caroline, whose bully father Bill actually holds her in a dungeon for 'vampire aversion therapy' of the most flagrant kind. Katherine puts Damon on feared Klaus's trail, so he can mount a rescue with Elena after putting her in her place.

In Chicago, Katherine meets Stefan in front of a store and she tells that Elena has the necklace that belongs to Rebekah. She also feels that Stefan is plotting a scheme against Klaus, but he does not share his plan with her. Meanwhile, in Mystic Falls, Anna shows up to Jeremy and talks to him that she is alone in the afterlife. Gloria seeks out the necklace using a spell while Bonnie and Caroline visit Elena; out of the blue, her necklace burns her chest. Damon is upset with people trying to change him to be Mr. Nice Guy. Sheriff Forbes asks him to compel Bill to forget everything but Bill resists. When Damon decides to kill Bill, Caroline protects her father. Meanwhile Gloria tortures Stefan to discover who is wearing the necklace but Katherine unexpectedly kills the witch. Stefan discovers that Klaus fears a vampire hunter, Mikael, and tries to get more information from Rebekah. She's suspicious of his attitude and tells this to Klaus, who decides to return to Mystic Falls.

Despite all that has happened, Caroline is determined to see that Elena, Bonnie, Matt and Tyler all enjoy a traditional Senior Prank Night before the school year begins at Mystic Falls High School. However, when uninvited guests show up, it doesn't take long for the evening to take a deadly turn. Damon convinces Jeremy that he can use his new connection to the other side to help find a way to defeat Klaus. Finally, Klaus deepens his hold on Stefan and uses him for increasingly violent and dangerous purposes.

Elena meets Stefan at the high school and he tells that he is watching her following Klaus's order. Rebekah, who is staying at the Salvatore's house, is in the same class as Elena. Elena plots with Alaric and Damon to lock Stefan in the dungeon of the Salvatore house. Tyler is fascinated and reveling in his sire bond to Klaus. Vicki convinces Matt to bring her back from the dead. Anna tells to Jeremy that darkness is surrounding Vicki, and that she has made a pact with the Original Witch. Vicki hits Matt on the head and seeks out Elena as part of her agreement with the witch. Meanwhile, Damon stays with Rebekah while Elena and Alaric abduct Stefan. Katherine awakens Mikael who confesses that he does not drink human blood, he instead feeds on vampires.

Damon, Alaric and Elena reach a hidden cage in the secret tunnel beneath the Lockwood mansion. Alaric studies the runes and primitive pictures, which indicate it was the home of an ancient Viking family, who interacted with the Original werewolf, vampires and witch. They confront Rebekah, who is shocked to tie it up with her memories of her family's youth, when their father Mikael, now the only hunter they truly dread, bullied his sons, especially Niklaus, leading in interaction with the originally friendly werewolf neighbors to family drama and the origin of vampires. After taunting Stefan, Damon releases him from Lexi's 'aversion therapy' and takes him along to seek Mikael's help. Alaric and Elena work out that Rebekah's memories don't take account of a last, crucial cruel twist.

The homecoming dance becomes the backdrop for a battle of lethal wits between Damon's party, including Mikael and Rebekah although not at all reconciled, and Klaus's, which fields the hybrids by diverting the party to the Lockwood mansion. Tyler surprises Caroline by stating he doesn't really mind being under Klaus's spell as hybrid, it's not worse than monthly lunatic agony as pure werewolf. Fearing even with the eternal oak stake in Mikael's hand Klaus may outsmart them, Damon secretly enlisted Katherine, but Klaus prepared the most stunning surprise.

Bonnie has weird dreams with four coffins. Jeremy hangs around with Tyler and invites him in his house. Stephan meets Bonnie and asks her to hide the coffins of Klaus's family. Klaus tries to force Damon and Elena to seek out Stephan and compels Jeremy to stand up in front of a pick-up driven by a hybrid in high speed without his ring; however Alaric saves him but has difficulties to recover. Jeremy kills the hybrid and he takes Alaric to the hospital with Elena. Damon meets Stephan and he tells that he saved Klaus to save Damon's life. Then Damon asks to participate in Stephan's plan against Klaus. Stephan accepts provided Elena does not know the plan. Elena makes a deal with Klaus and delivers Rebekah to him. Then she asks Damon to compel his brother to leave Mystic Falls.

Now Klaus has Elijah back, they host a dinner party to negotiate a future with the Salvatore brothers, who actually procrastinate. Meanwhile combined witchcraft finally opens the mystery coffin, from which a scary surprise guest is released, but both families will be shocked. Alaric has been wounded dangerously by lover Dr. Fell, who happens to be supernatural, which makes saving him problematic, but Elena steps up. Caroline's father Bill Forbes refuses to survive his vampire bite by allowing Caroline to turn him into one like her.

Now Klaus's original family's coffins are open, he's supplanted as family head by their sorceress-maker, mother Esther, who holds a grand ball in their splendidly restored mansion. Invitations with gifts and where needed other persuades go to the Salavtore brothers, Alaric, Matt, Caroline and especially Elena, who is asked for a private meeting. After Stefan prevents Damon from stopping her, she learns that Esther, aided by son Finn, needs Doppleganger blood to put a fatal spell on her children, the others being an 'abomination' except Elijah, firstly binding their fate. Tyler prepares his return.

After starting her day with a startling discovery of Damons' latest indiscretion, Elena is frustrated to find that none of her friends agree with her on how they should react to the Original family's internal power struggle. Once again caught up in the destiny of the Bennett witches, Bonnie and Abby find themselves playing a part in a ritual to appease the spirits of nature. When Elijah gives Damon and Stefan a dangerous ultimatum that puts Elena in danger, they turn to Alaric and Meredith for help with a plan that leads them to a terrible choice.

The present-day murders in Mystic Falls remind Damon of a similar crime spree a century earlier. Flashing back to 1912, Damon recalls a beautiful vampire.

Stefan still struggles desperately to get his blood-lust back under control. Damon keeps an eye on him, but has other priorities. Damon's former teacher Sage returns as his lover, in a secret pact against Rebekah, whom he seduces to keep an eye on her quest for the original white oak's sole known shoot. The old vampires are actually in league and torch the bridge made from its wood, fearing the weapon that could be made from it, but Damon stayed a step ahead. Dr. Fell tries to treat Alaric medically while Bonnie attempts to undo the curse which caused his hereditary madness, but they aren't careful enough, so Damon must intervene. Jeremy calls home from Denver, reporting that he only suffers from melancholy, but is doing well at school.

Stefan's emotional turmoil leads him to a dangerous confrontation with Klaus and, later to a heartbreaking moment with Elena. Claire Holt and Casper Zafer guest star

Caroline is thrilled when Tyler returns to town, but Tyler soon suspects that something has been going on between Caroline and Klaus. Matt tries to keep Rebekah (Claire Holt) busy.

The 1920s Decade Dance takes a deadly turn when Damon and Stefan realize they need the help of Matt, Jeremy and Bonnie to undo a spell that could be devastating for everyone.

Klaus acts on his intentions to leave town with Elena, but finds resistance from a surprising new enemy. Damon and Stefan have a surprisingly candid conversation about the future.

Determined to protect his sister, Jeremy makes a decision that will change everything; Bonnie makes a secret deal that has heartbreaking consequences.

In the fourth season premiere, Elena awakens after the accident to find the thing she dreaded most has come true. Damon is furious with Stefan, and takes out his rage on Matt.

Stefan and Damon argue about what is best for Elena. Jeremy and Matt are surprised to see a girl they used to know, April (GRACE PHIPPS), enrolling at Mystic Falls High.

Elena learns confronting Rebekah (CLAIRE HOLT) can be dangerous. Tyler gets a surprise visit from Hayley (PHOEBE TONKIN - The Secret Circle), a werewolf who helped him with Klaus.

At a fraternity costume party, Damon gives Elena a lesson in choosing a victim. Klaus reveals an encounter with a group of vampire hunters - flashing back to 12th century Italy.

It's a winter wonderland in Mystic Falls. Plus, Professor Shane (DAVID ALPAY) reveals a piece of ancient history that leaves everyone speechless.

Rebekah (CLAIRE HOLT) is back with a vengeance. Bonnie is uncomfortable when her father, Rudy Hopkins (RICK WORTHY - Supernatural), accepts the role of Interim Mayor.

Jeremy is furious when Klaus tries to control him by putting Matt's life in danger. Damon coaches Jeremy as he prepares to take on Klaus' new vampires, but they find that Kol has beaten them to it. Kol makes it clear that he will stop at nothing to convince everyone to give up the search for the cure. Looking for a new ally, Rebekah reminds Stefan that they were once close friends. When Sheriff Forbes and Mayor Hopkins question Shane about his involvement in the Founders' Council deaths, Bonnie steps in with questions of her own, and Shane's responses push Bonnie to the edge of her powers. Elena negotiates with Klaus to keep Jeremy safe, but when danger suddenly appears from a totally unexpected enemy, Elena comes up with her own daring plan for Jeremy.

When the 1980s Decade Dance at the high school is cancelled by Mayor Hopkins (RICK WORTHY), Stefan finds a charming way to make it up to a disappointed Rebekah (CLAIRE HOLT).

Shane (DAVID ALPAY) leads an expedition to a desolate island, where he believes the secret of the cure lies hidden. Rebekah (CLAIRE HOLT) and Elena continue their bitter rivalry.

Damon has an ugly run-in with a Hunter, Vaughn (CHARLIE BEWLEY - The Twilight Saga), and realizes he is one of the Five. Stefan admits his feelings about possibly becoming human.

Damon and Rebekah (CLAIRE HOLT) learn an unexpected bit of recent history from Vaughn (CHARLIE BEWLEY). Bonnie reveals the rest of Shane's (DAVID ALPAY) plan.

Elena's new outlook has everyone concerned. Damon and Rebekah (CLAIRE HOLT) work together, but his unwanted advice catches her off-guard. Klaus tries to use Hayley (PHOEBE TONKIN).

Realizing that Elena needs some time away from Mystic Falls, Damon takes her to New York City. Flashbacks reveal Damon's hedonistic life there in the 1970s.

While in a small town in Pennsylvania with Rebekah (CLAIRE HOLT), Elena has a surprising encounter with Elijah (DANIEL GILLIES). Klaus receives Caroline's reluctant help.

When Caroline's plans for the perfect Senior Prom night are disrupted by Elena, she turns to an amused Klaus for a solution. Bonnie makes a terrifying discovery.

Klaus returns to his past in New Orleans and meets with his former protégé, Marcel (CHARLES MICHAEL DAVIS), a charismatic vampire with control over the city's inhabitants.

The Salvatore brothers ask for backup from a surprising source when Elena calls their bluff. Katherine is suspicious when Bonnie makes her an offer.

Someone has been attacking patients at the hospital. A violent wind storm causes a power outage and ghosts suddenly appear - some with good intentions and some bent on revenge.

Season finale: It's Graduation Day. Damon's life is in danger and Elena faces an epic confrontation. Plus, Stefan discovers a horrifying clue to the mystery surrounding Silas.

As the fifth season opens, Elena, after a passionate summer with Damon, heads to college nearby with Caroline as her roommate. Plus, a terrifying appearance by Silas (PAUL WESLEY).

Back to Katherine's early life 1490, Nadia helps her mom with a fighting plan.