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.

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.

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.

Damon and Stefan try a brutal new approach to provoke Elena into turning her humanity back on, and Caroline is frustrated when her attempt to intervene backfires. When Elena figures out a way to call the Salvatore brothers' bluff, they call for backup from a surprising source. Matt gives Rebekah some unsolicited advice on her life choices, and she tries to help him in return. Caroline has a confusing and dangerous encounter with Klaus, and Katherine is suspicious when Bonnie makes her an offer that she promises will benefit them both.

Elena and Katherine both dream that Stefan is in danger and convince Damon to help them find him. But their plans are thwarted by a mysterious woman who seems to know everything about Stefan's past and Damon's disturbing future.

Dr. Wes gives Katherine some disturbing news. Jeremy and Bonnie share a glimmer of hope after talking with Amara. Silas fails to keep a promise which causes Damon to turn to Tessa for help with his new plan. Stefan makes a heartbreaking confession to Damon and Elena.

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.

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.

When the past comes back to haunt her, Elena is forced to face her problems head on. After a night out at the annual Whitmore Medical Center Fundraiser, Jo opens up to Alaric about her own tragic past. Meanwhile, Stefan, Matt and Enzo resort to extreme measures when Tripp withholds information about his vampire-killing operation, and Caroline is in a race against the clock when Sheriff Forbes gets caught in the middle of a dangerous plan. Elsewhere, Tyler and Liv grow closer, and Damon stumbles upon a startling clue that renews his hope.

When Liv and Luke’s father arrives to town to celebrate their birthday, they try and convince him to let Jo and Kai take their place in the merge ceremony. After Tyler finds out that the merge is happening sooner than he expected, he urges Liv to let him talk to her father. Meanwhile, after Caroline’s plan to cure her mother takes an unexpected and devastating turn, Elena, Stefan and Damon gather at the hospital, while Jo attempts to save Sheriff Forbes’ life. Lastly, with the merge set to take place, Damon’s risky plan quickly sends things spiraling out of control, forcing one of the twins to take matters into their own hands.

As Alaric and Jo reluctantly participate in their bachelor and bachelorette parties, Damon and Elena discuss the ramifications from an impulsive offer that Damon makes. Unsure of what to do, Elena turns to Bonnie and Jo for advice, but is left conflicted when Bonnie raises some unanticipated concerns. When Enzo realizes Lily is on a dangerous downward spiral, he asks Stefan to help intervene before it’s too late. Lastly, fed up with the supernatural threats that plague their town, Matt takes his frustrations out on Tyler, while Alaric considers a life-changing piece of advice.

After realizing the downward spiral he was on, Damon decides he’s going to turn over a new leaf and that his actions moving forward will do right by Elena. Lily prepares for the arrival of a special figure from her past, while Enzo stands by not sure what to expect.

Elsewhere, at Caroline’s urging, Stefan comes face-to-face with Valerie and learns some upsetting details about her past, while Enzo and Bonnie find themselves at odds when they’re forced to fend off a violent threat. Finally, when Bonnie learns some disturbing information involving the Phoenix stone, she is forced to confront Alaric.

When his experience in the Phoenix stone leads him to do the unthinkable, Damon finds himself without a care in the world, spiraling out of control and under the influence of a dangerous and reckless Julian. Refusing to give up on his brother, Stefan attempts to reason with Damon only to uncover the devastating reason for his descent.

Elsewhere, Caroline begins having some dangerous side effects as a result of her supernatural pregnancy and is forced to turn to Valerie for help. Meanwhile, Bonnie, Nora and Mary Louise attempt to track down a ruthless vampire hunter named Rayna after they suspect that she has reemerged.