Elena puts herself in a dangerous position as she searches for the truth about Katherine's past and what her own future may hold. Knowing that Stefan would never agree to her plan, Elena swears Caroline to secrecy. Damon uses a new-found confidant to help him try to discover the real purpose and power of the moonstone. Jeremy and Bonnie meet Luka, a new student with a surprising family history.
Elena decides to take matters into her own hands and offers a tempting incentive to Rose for her help. When things take an unexpected turn, however, Rose calls on Damon to deal with the plan Elena has set in motion. Jeremy's reckless attempt to help Bonnie retrieve the moonstone lands him in a life-threatening position and forces Stefan to put himself in danger. Bonnie and Luka form a closer connection. Tyler shows Caroline the Lockwood cellar, where she makes a discovery that leaves them both terrified.
Klaus and Stefan arrive in Chicago, where Stefan is reunited with a vampire who hasn't really moved on from her interest in him decades earlier. In a flashback to Chicago in the 1920s, Stefan comes face-to-face with a shocking chapter from his wild past. After Damon gets a tip on Stefan and Klaus' whereabouts from an unexpected source, he and Elena follow their trail. Back in Mystic Falls, Tyler is concerned about Caroline and turns to Sheriff Forbes for help.
Still in Chicago, Klaus enlists the help of a witch called Gloria to try to discover why his plan is not working. Gloria's spells reveal some intriguing glimpses of the truth but she soon realises she need Stefan to complete the puzzle. Back in Mystic Falls, a new enemy pushes Damon over the brink with devastating consequences, while Caroline struggles with her own emotional issues.
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.
On the first day of their senior year, Elena, Caroline, Bonnie and Matt are still reeling from recent events, while Tyler seems to be enjoying everything a little too much. Damon is annoyed by a new houseguest, and everyone is surprised by the arrival of a new student in Alaric's history class. Matt asks Bonnie for help when he realizes he made a serious mistake. Meanwhile, Stefan continues to carry out his latest assignment from Klaus.
As Mystic Falls prepares to celebrate the traditional Illumination Night, the town is invaded by spirits of the dead. After a particularly violent encounter with an angry spirit, Damon asks Bonnie to find the reason behind the ghosts' surprising power. Elena convinces Jeremy to use his connection to the other side to help her find a new way to reach Stefan, leading Jeremy to a terrible choice. Finally, Alaric discovers a long-hidden clue to the past.
With help from Elena and Bonnie, Alaric tries to decipher the meaning behind his recent discovery Elena and Rebekah engage in a mean-girl power struggle, until Rebekah finally reveals some of her family's ancient secrets and the violent past she shares with Klaus and Elijah. Damon tries a reckless new approach to make a breakthrough with Stefan, and they're both surprised by an unlikely ally.
On the night of the Homecoming dance, Rebekah opens up to Elena about why the evening is so important to her, leaving Elena with conflicting emotions. Caroline and Matt are both shocked at Tyler’s behavior throughout the evening. The night takes a surreal turn when Klaus puts his latest plan into action. Determined to outsmart Klaus, Damon enters into a dangerous partnership, leading to a terrifying turn of events.
Stefan has hidden the coffins containing the bodies of Klaus’ family, and Klaus quickly turns to violence to convince Damon and Elena that no one will be safe until he finds Stefan and gets his family back. Tyler continues to make the most of his new abilities as a hybrid, but he has to face the disturbing consequences of his actions as well. After a terrifying incident, Elena and Alaric grow increasingly concerned about Jeremy’s attitude and, ultimately, his safety. Alaric meets the beautiful Dr. Fell, who is intrigued with his amazing ability to heal. While trying to strike a deal with Klaus, Elena delivers news that truly shocks him.
Although Caroline is in no mood to celebrate her 18th birthday, Elena, Bonnie and Matt surprise her with a small party in an unusual location. Damon and Stefan disagree on the best way to handle Klaus , and a reckless Stefan decides to test his theory by taking things to dangerous extremes. Bonnie is concerned when Elena tells her about Jeremy's new plans. At a Founder's meeting, Alaric once again runs into Dr. Fell, who is in the middle of an argument with her ex-boyfriend, the medical examiner. Tyler refuses to go along with Klaus' latest demand, and is surprised when Klaus seems to accept his decision.
Prophetic dreams about the mysterious fourth coffin lead Bonnie and Elena to a surprising source, while Tyler seeks help to break free from Klaus' bond so he can be with Caroline. Alaric's new friend Dr. Fell has a secret no one sees coming, and Stefan's interference in Elena's life reveals something that surprises even him.
Sheriff Forbes delivers some disturbing news to Alaric and Elena about the weapon used in a recent murder. In the Salvatore brothers’ escalating quest to kill Klaus, Stefan turns to Bonnie and Abby, while Damon reaches out to an old acquaintance for help in setting up an elaborate plan. Intent on a plan of his own, Klaus hosts a strange dinner party, where he reveals another story from his family’s violent past until an unexpected guest brings the party to an end. Meanwhile, Caroline is heartbroken when she is unable to stop a tragedy from unfolding.
Elena is surprised to receive an invitation to a formal ball, and when Damon and Stefan hear the party is being hosted at Klaus’s newly renovated mansion, they both insist on attending the event with her. Caroline and Matt also receive invitations to the ball from unexpected admirers. At the elegant party, Elena learns of a horrifying plan that could lead to numerous deaths and she must decide who she can trust with her new information. Caroline discovers a side of Klaus no one would have suspected. Finally, after an evening of violence and dashed hopes, Damon finds a new way to cope.
After starting her day with a startling discovery of Damon’s 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.
A century after their first encounter, Damon and Sage meet again at the ceremony to kick-off the restoration of Wickery Bridge. Damon is surprised to learn the reason Sage has returned, and pleased when she devises an unusual method to help him figure out what Rebekah is up to. Abby is having a hard time adjusting to her new reality, despite Bonnie and Caroline’s efforts to help. When Damon informs Elena of Stefan’s latest struggles, she reaches out to Stefan to help her save a friend in danger, in hopes that it will help bring Stefan even closer to his humanity. Finally, when Damon discovers a new secret weapon, he lets Stefan in on the news.
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. Elena tries to negotiate with Klaus to keep Jeremy safe.
Elena meets a sad and secretive student on campus. Elena and Damon attend the Whitmore Historical Ball dressed as Anne Boleyn and Henry VIII. While there, Elena receives a disturbing message from Dr. Maxfield. Nadia reveals her surprising history to Katherine;. Silas demands that Damon commit an unthinkable act.
Caroline convinces Elena and Bonnie to attend Whitmore College's Bitter Ball for broken-hearted students. Bonnie meets a fellow student who appears to be dabbling in witchcraft. Tyler worries about Matt's relationship with Nadia. Damon and Enzo resort to violence to convince Bonnie and Jeremy to help them get revenge, but their plan takes a horrifying turn.
Damon's behavior escalates from destructive to deadly. Stefan begins to regret their last conversation and tries to track Damon down and intervene. Dr. Wes enlists the Travelers to set a trap that will test Damon's friendship with Enzo; and a talk between Caroline and Stefan leads to a horrifying realization.
Stefan and Elena become stranded in a remote location, after escaping from Markos, and he gets philosophical about her relationship with Damon. Damon sets a trap for Markos. Bonnie admits that she's been keeping the truth about the Other Side from everyone. Caroline witnesses an unthinkable act of violence by one of the Travelers.
Elena comes to terms with the loss of Damon with the help of Alaric. Enzo convinces Caroline to join him as he tracks down Damon and Bonnie. Meanwhile, Matt worries about Jeremy who is spending time with Sarah, a mysterious girl who has recently arrived in Mystic Falls. Elsewhere, Tripp, leader of the community protection program, tells Matt about his connection to the town. Lastly, with the Other Side destroyed and gone for good, Damon and Bonnie reluctantly band together to uncover the mystery of where they are and how they are going to get back home.
Bonnie tries to replicate her favorite traditions, while reminiscing about happier times with her friends; Sheriff Forbes brings holiday cheer to Caroline at Whitmore College; Alaric turns to Damon and Elena for help when Jo goes missing; Tyler approaches Liv and Luke with a risky plan; Jeremy helps Matt carry out a plan to take down Enzo; Stefan is forced to break some devastating news to Caroline.
In the aftermath of a clever plan orchestrated by Lily, Damon sets off on a road trip with Bonnie and Alaric in search of leverage they can use against his mother. Meanwhile, Caroline, who is being held hostage by the Heretics, learns some shocking information about Valerie’s past, while Stefan learns a few unexpected details about his own past from Lily. Finally, Alaric turns to Bonnie for her help after coming clean about a secret he’s been keeping.
After being reunited with her former love Julian, Lily hosts a dinner party to introduce him to Damon and Stefan and to declare peace between her family of Heretics and the residents of Mystic Falls. Damon and Stefan find themselves at an impasse when they realize they have differing views on how to handle Julian’s arrival. At the party, Bonnie and Matt uncover a strange mystery involving some unsuspecting residents, while a devastating revelation causes Alaric to reach his breaking point.
In the aftermath of his brother’s fateful decision, Stefan awakens to find himself thrown into a life or death situation with only his basic instincts to rely on. With time working against him, he sets off on a journey of survival. Meanwhile, desperate to save his brother, Damon follows an unusual lead he has come across, while Matt sends Valerie to Dallas to enlist Alaric’s help in the search for Stefan. Finally, when Rayna discovers the emergence of a new threat, she sets off on her own mission to find Stefan before the others do.
Determined to capture an escaped vampire named Ambrose, who may be the key to getting Stefan back safely, Damon heads to Memphis with Alaric in tow. However, reluctant to step back into his former vampire hunting ways, Alaric makes his unwillingness to participate clear, while revealing the truth about the past three Damon-less years of his life. Meanwhile, in the psych ward, Bonnie meets a young woman named Virginia, who provides her with some valuable information about why The Armory may be after her. Finally, Enzo takes matters into his own hands when he learns some devastating news from Rayna.
When Enzo’s efforts to protect Bonnie end up putting her life in jeopardy, they learn that Rayna may hold the key to her survival. With time running out and Rayna at the reins, Enzo and Bonnie reluctantly team up with Damon, who is desperate to save Bonnie’s life and to repair their broken friendship. Elsewhere, when Stefan travels to Dallas and comes face to face with Alaric, tensions escalate and they are forced to confront the fallout from Stefan’s absence in Caroline’s life. Finally, Enzo learns The Armory’s true motives behind their search for Bonnie.
With Bonnie’s life at stake and an uphill battle ahead of them, Damon and Enzo lead the charge to save Bonnie before her condition worsens. Stefan reluctantly teams up with Matt for the sake of Bonnie and uncovers the truth behind Matt’s anger towards him. Elsewhere, determined to help her best friend, Caroline joins Alaric on a mission and quickly realizes how much she’s missed her former supernatural lifestyle. Finally, after their plan takes an unexpected turn, Damon makes a fateful decision that will forever change his relationship with Bonnie.
The transfer of Rayna's life also turns Bonnie into a huntress, who must turn on all her supernatural friends, but fights that, hating only Damon, by inducing herself in a deep sleep, merely slashing in nightmares. So the vampires try to intrude her dreams and find a way out. Caroline sends Alaric home and goes first, but not only fails, she actually gets marked up as fatal target. Nevertheless, Enzo and the brothers take the same risk, to little avail. Sheriff Matt has his own mission.
Despite their best efforts to help Bonnie through the harrowing predicament she now faces, Damon, Enzo and Caroline realize their options are running out and drastic measures need to be taken. With their only chance of saving their friend lying inside the Armory, Stefan breaks the news to Caroline that they may need help from an unlikely source – her and Alaric’s twin daughters. Elsewhere, Enzo keeps Bonnie preoccupied by bringing her back to their cabin but when his plan takes an unexpected turn, it’ll be up to Damon to make the ultimate sacrifice to save his closest friends.
As Enzo continues to fight the control over him, Bonnie finds herself at the center of a deadly game and forced to make a heart wrenching decision involving two of the most important people in her life. At the Armory, Alaric researches a mysterious artifact that he hopes will help in their fight to get Damon and Enzo back. Finally, Damon’s downward spiral leads him to Tyler Lockwood who attempts to talk some sense into him before it’s too late.
Tasked with finding a mysterious artifact, Damon’s latest mission takes him to Texas where a violent run-in with Peter Maxwell leads to a surprising revelation. Meanwhile, after gaining the upper hand in their fight to save Damon and Enzo, Stefan and Alaric team up and uncover the origins of the mysterious force they’re up against. Finally, Matt returns to the fray after his past and present collide in an unexpected way.
When her children become the focus of the Siren’s latest plan, Caroline takes drastic measures to ensure nothing gets in the way of keeping her family safe. In a race against the clock, Stefan pledges to do everything he can to save the twins, while tensions between Alaric and Caroline boil over, leading them to face some harsh realities about the future of their family. Meanwhile, when Enzo finds himself unable to fight off Sybil’s latest move, Stefan dives into his subconscious and along the way, sets off a chain of events that leaves him faced with a life-changing decision.
Faced with the fallout from his interaction with Cade, Stefan is determined to have one thing go right – Christmas Eve with Caroline. However, when Damon and Sybil crash their Christmas Eve dinner, which had been joined by Alaric, Matt and Peter, things quickly take a dark and twisted turn. Meanwhile, in a series of flashbacks to Stefan’s past, Cade’s attempt to entice him with his mysterious agenda leaves Stefan faced with an unimaginable decision.
Stefan and Damon attend an anger management support group looking for their next victim. Sybil is still alive and teaching a group of high school students who she’ll later use as leverage to get Caroline to locate a historical artifact that can be used against her. Meanwhile, Stefan and Damon continue their commitment to Cade as they test the morals of a young doctor, Tara.