Season 1
The first part of the season focuses on the introduction of the vampires, specifically the lives of the vampire brothers Stefan and Damon Salvatore who return to their birth town after a long period of absence, Stefan wanting to be the first to conquer the heart of Elena, and Damon wanting to revive his long-lost love Katherine, Elena's doppelganger, trapped in a tomb. It also deals with Victoria "Vicki" Donovan's transformation into a vampire and her death. Later, Anna makes an appearance. She is a vampire who came to town around the Night of the Comet, and planned to open the tomb to save her mother Pearl, but accidentally also frees the other vampires in the tomb. The second part of the season introduces the released tomb vampires, although Katherine isn't among them. They end up meeting up with Pearl and Anna, who are housing all the tomb vampires to "take back" their town. John Gilbert is also introduced, who is Elena's biological father, and plans to use using the Gilbert device to destroy all the tomb vampires. The season concludes with the celebration of the town's founder's day, ending the battle of the tomb vampires and greets the final return of Katherine.
Season 2
The second season mainly focuses on the arrival of Elena's doppelganger Katherine Pierce and the reasons she returned to Mystic Falls. The second season also introduces werewolves. Tyler's Uncle, Mason Lockwood, reveals as a werewolf, arrives in the town after the death of his brother, Tyler's father, and tells Tyler about the so called "Lockwood curse" that has run in their family for centuries. He tells Tyler that in order to activate the curse, more specifically to activate the "werewolf" gene, the person must kill someone. Katherine turns Caroline into a vampire, after Caroline ingested Damon's blood to heal from the accident, so she can have a spy against Stefan and Elena, using Matt to scare Caroline into helping her. Tyler accidentally kills an innocent girl after Katherine compelled her to provoke him. Katherine's main reason for returning to Mystic Falls was to find the moonstone, with the help of Mason, who is later killed by Damon. Katherine falls back on Plan B and calls in a favor from a witch named Lucy to help her get the stone back from Stefan and Damon. Lucy casts a spell on Elena and Katherine, meaning that when Katherine is hurt, it also affects Elena. When Lucy finds out another Bennett is at the party and Katherine had deceived her, she puts a spell on the moonstone, injuring Katherine. Damon then leaves her in the original tomb, where he believes she belongs. She tells him the reason she hasn't killed Elena is because she is in danger and needs protection. Damon ignores her and leaves her in the tomb, thinking she's lying. Elena is later kidnapped, showing that Katherine had been telling the truth. Elena is held hostage by two 500-year-old vampires, Rose and Trevor, who have been on the run from the Originals-the first generation of vampires. Rose reveals to Elena that she is the Petrova doppelganger and needs to be sacrificed to break the sun and the moon curse. Katherine was also a Petrova doppelganger who used Trevor to help her escape from the Originals and Rose to turn her into a vampire to save herself. Elena is rescued by Stefan and Damon before Elijah, an Original, can take her away.
Klaus, the oldest vampire in history, is now hunting for Elena. Klaus wants to break the curse before the werewolves can. Elijah has made a deal with Elena to continue living her life instead of trying to hand herself over to Klaus. That way, he will protect her loved ones because he wants to use Elena as bait so he can lure out Klaus and kill him. Elena agrees to do so, and gives Elijah one more condition: he must free Stefan from the tomb, and Elijah accepts. Jules, a friend of Mason, comes into town informing the Lockwoods he never came back to Florida and reports him as a missing person. Alaric is suspicious and calls Damon to the Grill. They try various methods to trick Jules into revealing if she is a werewolf or not, but Jules eventually reveals that she is indeed a werewolf, and could "sniff out" that Damon is a vampire and the wolfsbane Alaric put in her drink the whole time. Damon tells Jules she won't find Mason and to leave town. She tells Damon it's stupid of him to threaten her during a full moon and that he's been "marked." Later, Jules breaks into the Salvatore mansion in wolf form and attacks Damon, but Rose pushes him out of the way, getting bitten instead. As Rose succumbs to the effects of her wolf bite, Damon stakes her into a peaceful death, as Jules says a stake to the heart is the only cure.
Uncle John's return to Mystic Falls comes as an unpleasant surprise to Elena, Damon, Jenna, and Alaric. John reveals to Damon that the only way to kill an Original is with a dagger dipped in white ash wood, which dates back to the Original's beginning. John is still working with Katherine and has a plan to get her out of the tomb. After being put under a hypnosis spell by Bonnie, Luka reveals that he and his dad are working for Elijah because Klaus has his sister and they want him dead as well. Luka says that Klaus will be weakened by the sacrificial ritual, meaning Elena has to die so Elijah can kill him and set his sister free. Stefan figures out that Elena knew about Elijah's plans for her, telling her she's being a martyr and not heroic. John gives Damon the dagger with the ash from the white oak so he can kill Elijah. Elena finds more of John Gilbert's journals and finds out that if a vampire uses the dagger, he will die as well. Stefan warns Damon in time and Alaric uses the dagger to stab Elijah, but he pulls the dagger back out, which means Elijah isn't really dead. He shows up at the cabin Elena and Stefan are staying at and tells Elena their deal is off. Elena threatens to turn herself into a vampire if Elijah doesn't honor their deal, but he doesn't believe her. She stabs herself in the stomach. Elijah panics and agrees to protect her friends and family and begs her to let him heal her. When she comes forward so he can give her some of his blood, she stabs him with the dagger and leaves it in him. Elijah's death means Katherine is no longer compelled to stay in the tomb and she returns to Damon and Stefan's house where she says she'll stay and help them take down Klaus. She helps in killing the Martin witches when they try to bring Elijah back to life and also when Jonas tries to kill Elena. But when Isobel returns to town, Katherine double crosses the Salvatores by kidnapping Elena and stealing the moonstone for Klaus in exchange for her freedom. But it is revealed that Klaus wanted Katherine and compelled Isobel to get her and the moonstone. When Klaus comes to town, he enters Alaric's body and keeps Katherine with him. He compels her to stay in Alaric's house. Bonnie and Jeremy find the site of the witch massacre with Damon's help and Bonnie channels all the power. The Alaric-Klaus blends with Stefan, Damon and Elena and finds out that Bonnie has her powers. Then he tries to kill Bonnie by making her summon all her powers. Damon tells Bonnie to put a protection spell and make Alaric-Klaus believe that she is dead. Elena does not want Bonnie to die while killing Klaus, so she pulls the dagger out of Elijah's heart. After Elijah comes to life, Elena learns the full history of Klaus. She finds out that the Aztec curse is fake and that there is a curse on Klaus as he is a vampire born in a werewolf bloodline.
Season 3
More about Klaus and The Original Family as his motives for wanting Stefan on his side will be revealed during season three. Stefan becomes darker, Damon and Elena struggle with the guilt of their growing bond even as they work together to bring Stefan back. Caroline and Tyler grow closer, causing a war between their two families. Ghosts from Jeremy's past have a message for him, and begin to affect his relationship with Bonnie.
The first episode of the season will feature Elena's 18th birthday, "There will be a small time jump [from where last season ended] as we celebrate Elena's birthday. But as is the pattern in Mystic Falls, the event never reaches its climax." exec Julie Plec said in an interview with TV Guide She also revealed that Elena will have to deal with her attraction towards Damon over the course of the season
