The second season begins with Elena discovering her uncle John's bloody body and learning Jeremy's fate, and Damon realizing that Katherine has returned. Meanwhile, Caroline is taken to the hospital following a car accident, and Tyler's mysterious uncle Mason arrives in town.
When a confused and desperate Caroline leaves the hospital and joins her friends at the Mystic Falls Carnival, Damon wants to take immediate action, but Stefan and Elena come to Caroline's defense. Matt is completely mystified by Caroline's behavior, but still tries to tell her about his feelings for her.. Damon has suspicions about Tyler's Uncle Mason and uses Tyler's volatile personality in an attempt to get Mason to reveal his secret. Upset with everything going on around her, Bonnie takes her anger out on Damon.
Elena, Damon and Alaric take a road trip to Duke University and search through Isobel's research on folklore and paranormal phenomena to see if they can uncover any clues to the mystery surrounding the Lockwood family. Isobel's former student, Vanessa offers to guide them through the research and ends up getting quite an education herself. Stefan comes face to face with a terrifying new danger in the woods, and Tyler makes a shocking discovery about Mason... .
Stefan takes drastic measures to find out the real reason Katherine has returned to Mystic Falls, and is shocked when she reveals new secrets about what really happened in 1864. Damon tries a new tactic to resolve his issues with Mason,... . but it proves costly. Tyler pushes Mason to tell him the truth about the Lockwoods. Finally, when Katherine delivers an ultimatum, Stefan and Elena are left with very few options.
Tyler learns more about the Lockwood family curse from Mason. Stefan and Damon argue over how to handle Mason. Elena tries to keep Jeremy from becoming more involved with the Lockwood mystery, but Jeremy makes an effort to hang out with Tyler. Mason gives Sheriff Lockwood some startling information, leading to a night of violence, confession and heartbreak.
Despite Elena's efforts to keep Jeremy safe, he offers to help Damon and Alaric deal with Katherine... Sheriff Forbes and Caroline share a few rare moments of quality mother/daughter time. Bonnie accidentally discovers new information about Mason and shares it with Stefan, leading Damon to take matters into his own hands.
Stefan and Damon decide on a new plan to deal with Katherine at the Lockwood's masquerade ball. Katherine calls on an old friend, Lucy, to attend the ball with her.
Bonnie, Jeremy and Alaric all do what they can to help Stefan and Damon, but Katherine has a surprise planned that none of them could foresee. Things take an ugly turn when Matt and Tyler start doing shots with their friends.
An Ancient Presence In Mystic Falls, Stefan and Damon come to Elena's assistance and, in the process, learn surprising new information about people, vampires and events in the distant past. Jeremy helps Bonnie after she casts a difficult and exhausting spell, and Caroline does what she can to make things easier for Tyler. Finally, Stefan and Damon reach a new understanding.
Katherine'spast is finally revealed when Elena puts herself in a dangerous position as she searches for the truth about what her own future may hold.
Jeremy teams up with Bonnie after she casts a difficult spell. Stefan and Damon both come to Elena's assistance, and in the process, learn some information about vampires, people and events in the distant past. The brothers also come to reach a new understanding. Meanwhile, Caroline tries to make things easier for Tyler.
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.
As the full moon approaches, Caroline helps Tyler prepare for the transformation he is powerless to stop. While Stefan and Katherine play mind games on one another, Damon and Alaric are suspicious when a stranger named Jules shows up in Mystic Falls, searching for her missing friend, Mason. Elena is frustrated at the lengths Jeremy and her friends have gone to in order to keep her safe. Bonnie and Luca work together on a spell, while still keeping secrets from one another. Finally, Elijah makes an unexpected appearance with an offer that could change everything.
Stefan and Alaric try to find Isobel to ask her about Klaus, but useless. Elena and Rose are having a sincere conversation, speaking about her feelings to both brothers. Damon tries a lot to break the werewolf curse and save Rose, while she's dying painfully and is a threat for everyone in a town. Some new facts about Jules come out making everyone a bit afraid of her. Caroline is uncertain about her feelings for Tyler and wants him to be a good friend only for some time. Everything changes when someone dies.
Johnathan Gilbert's return to Mystic Falls comes as an unhappy surprise to Elena, Jenna and Damon. Caroline lets Stefan know about her conversation with Tyler, and Stefan does his best to reach out to a confused and conflicted Tyler. Jeremy comforts Bonnie after her disturbing conversation with Jonas... When Jules takes a hostage, the situation quickly escalates into a unhappy confrontation.
Stefan and Elena get away for what they hope will be a romantic weekend at the Gilbert family lake house, not realizing that they've been followed. Jenna starts to worry that Alaric isn't being honest with her. Jules explains the importance of the sun and moon curse to Tyler, but leaves out an important detail. Damon attends a tea at the Historical Society in order to talk to Elijah, but Elijah isn't giving up any secrets. With help from Caroline and Jeremy, Bonnie uses deceptive measures to get shocking new information out of Luka. Finally, Tyler offers Matt some relationship advice.
Stefan tells Elena about a dark time in his history and the surprising person whose influence changed everything. After getting the truth out of Luka, Jonas makes his feelings clear to Bonnie and Jeremy. Trying to catch Elijah off-guard, Damon arranges a dinner party for him with Jenna, Alaric and Andie, but last-minute information throws Damon's plan into chaos.
Katherine's mind games are getting on everyone's nerves, but Damon, Stefan and Elena realize that her knowledge of Mystic Falls history will help them stay alive. Frustrated with her relationship with Matt, Caroline finds a new way to get his attention. Alaric makes a surprising confession to Jenna, and Katherine makes a different kind of confession to Damon. Stefan and Bonnie try to convince Jonas and Luka that they should all be working together, but Jonas' lack of trust leads to a unhappy and fiery confrontation.
Elena and Alaric both lash out at John when Isobel's unexpected arrival leaves Jenna devastated. Bonnie works with Damon and Jeremy to find the spell they'll need to harness her ancestors' power. A heartbroken Caroline doesn't know what to do about Matt. Stefan and Damon realize they have a new secret weapon.
As the high school prepares to throw a "1960s Decade Dance", Elena starts receiving disturbing messages from Klaus via an unusual source. Bonnie tries to reassure Jeremy that she is strong enough to help Elena, but a worried Jeremy asks Stefan for advice. Caroline talks Matt into taking her to the dance. Expecting Klaus to show up at the dance, Damon and Alaric attend as chaperones, but Klaus is playing a complicated game that keeps them on edge. Finally, Damon comes up with a new plan of action that shocks and upsets everyone.
Stefan and Damon are furious when they discover that Elena has defied them both to make a new ally and take control of the plan to out-maneuver Klaus. Disagreement over how to protect Elena leads to growing tension between the Salvatore brothers. Meanwhile, Stefan has his hands full trying to keep a confused and frightened Jenna safe. Flashbacks to 1491 reveal Katherine's introduction to Elijah and Klaus, along with the origin of the moonstone curse. Elena learns shocking new information about Klaus' motives.
Damon is willing to go to extraordinary lengths to prevent Elena from being a victim of Klaus' plan to break the curse. Damon's actions put him at terrible odds with Stefan and the tension that started brewing between the brothers over their differing opinions of how to help save Elena's life blows up into full-scale conflict. Tyler returns to Mystic Falls after receiving a disturbing phone call. With the full moon marking the arrival of the sacrifice ritual, Stefan and Elena spend a romantic day together - afraid it might be their last.
With the arrival of the full moon, Elena tries to prepare for whatever Klaus has planned and Tyler faces his second transformation. The terrifying events quickly spin out of control, despite an unexpected act of courage. Finally, Damon admits the truth to Stefan about a terrible new development they must face.
While Mystic Falls presents a screening of "Gone with The Wind" in the town square, Damon's memories of Katherine in 1864 mix with the reality of Elena in the present day. Stefan pays a terrible personal price for his attempt to prevent a tragedy, and Sheriff Forbes makes a deadly mistake while trying to keep everyone safe. More than one life hangs in the balance as the consequences of the sacrifice ritual play out to a horrifying conclusion.