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.

Elena and Damon set off together to make sure Jeremy is safe in Denver, and to see if his special abilities can help reveal the information they need about ancient vampire bloodlines. It doesn’t take them long to learn that Jeremy has been hanging with the wrong people. Stefan and Klaus both go to brutal extremes in their search for the missing weapon. Caroline is thrilled when Tyler returns to town, but Tyler soon suspects that something has been going on between Caroline and Klaus. Matt has his hands full trying to keep Rebecca busy organizing the school’s upcoming 1920s Decade Dance.

Appearing unexpectedly at Mystic Falls High, Rebekah wastes no time trying to force Stefan, Elena and Caroline to answer her questions about the search for a cure, leading to a bombshell piece of information from Elena. When Bonnie’s father, Rudy Owens, accepts the role of Interim Mayor, he makes it a priority to protect his daughter, who isn’t at all comfortable with the role he suddenly wants to play in her life. Professor Shane continues to encourage Bonnie to believe in her powers, but he soon finds himself in danger when he reveals too much to the wrong person. Later, Caroline does her best to comfort Tyler after a violent confrontation. Meanwhile, at the lake house, Damon and Matt train Jeremy, trying to raise his game as a hunter, but Klaus is impatient with their progress and intervenes to speed up the process.

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 Rebekah turns down Klaus’ plea to stop Kol and protect Jeremy, Klaus turns to Stefan for help. After an angry confrontation with her father, Mayor Hopkins, over his unconventional approach to ending the violence in Mystic Falls, Bonnie has a frightening run-in with Kol, followed by an unexpected visitor. Klaus complicates the already tense feelings between Stefan and Damon by revealing a bit of Stefan’s personal life, then surprises Damon by asking for personal advice. Elena tells Stefan about her dangerous plan for Jeremy, leaving Stefan in a difficult spot. When the high school’s 1980s Decade Dance is cancelled by Mayor Hopkins, Stefan finds a charming way to make it up to a disappointed Rebekah.

As Graduation Day approaches, Caroline tries to distract Elena by focusing on simple tasks like sending out announcements, but Elena won't be swayed from her new obsession. Sheriff Forbes calls Damon and Stefan to the hospital, where someone has been attacking patients. Still trying to force Katherine to help her, Bonnie refuses to give up on her plan to defeat Silas. As a violent wind storm causes a power outage in Mystic Falls, ghosts suddenly appear - some with good intentions and some bent on revenge.

On Graduation Day, Mystic Falls is overrun with ghosts intent on settling old scores and fulfilling their supernatural destinies. Damon’s life is in danger after a ghostly encounter, while Matt and Rebekah join forces to battle a ghost determined to find the cure. As everyone gathers for the graduation ceremony and the ghosts converge, help comes from an unlikely hero. Caroline receives a touching and unexpected graduation present, and Bonnie’s plan leads to the closing of the veil. Elena makes a decision about the Salvatore brothers and faces an epic confrontation with Katherine. Finally, Stefan discovers a horrifying clue to the mystery surrounding Silas.

Stefan and Elena experience unsettling dreams of the life they might have had together. Bonnie has a disturbing encounter with Grams. Enzo searches for a woman he loved decades ago. Bonnie learns that Jeremy is working with Liv. Matt has a terrifying encounter with inhabitants of the Other Side.