Katherine Pierce

Damon and Alaric try to stop John Gilbert from setting a plan in motion to bring Founder's Day to an end amid chaos, destruction and death.

Elena comes home to a nightmare; Damon realizes Katherine has returned; Tyler receives a surprise visit from his uncle.

Katherine recalls the past.

Stefan and Damon decide on a new plan to deal with Katherine at the masquerade ball.

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.

Stefan and Damon are angry when they find out that Elena has taken matters into her own hands in the battle against Klaus. Tensions also rise between the brothers over the best way to protect her.

In Chicago, Katherine meets Stefan in front of a store and she tells that Elena has the necklace that belongs to Rebekah. She also feels that Stefan is plotting a scheme against Klaus, but he does not share his plan with her. Meanwhile, in Mystic Falls, Anna shows up to Jeremy and talks to him that she is alone in the afterlife. Gloria seeks out the necklace using a spell while Bonnie and Caroline visit Elena; out of the blue, her necklace burns her chest. Damon is upset with people trying to change him to be Mr. Nice Guy. Sheriff Forbes asks him to compel Bill to forget everything but Bill resists. When Damon decides to kill Bill, Caroline protects her father. Meanwhile Gloria tortures Stefan to discover who is wearing the necklace but Katherine unexpectedly kills the witch. Stefan discovers that Klaus fears a vampire hunter, Mikael, and tries to get more information from Rebekah. She's suspicious of his attitude and tells this to Klaus, who decides to return to Mystic Falls.

While in a small town in Pennsylvania with Rebekah (CLAIRE HOLT), Elena has a surprising encounter with Elijah (DANIEL GILLIES). Klaus receives Caroline's reluctant help.

Season finale: It's Graduation Day. Damon's life is in danger and Elena faces an epic confrontation. Plus, Stefan discovers a horrifying clue to the mystery surrounding Silas.

When Elena and Katherine have the same dream that Stefan is in danger and desperately needs their help, they convince Damon to help them find Stefan. However, their plans are thwarted by a mysterious young woman named Tessa who seems to know everything about Stefan's history. In flashbacks to a distant time and place, Tessa reveals the shocking secrets in her past and what she has planned for the future. She also has a disturbing message for Damon about his own future. Silas forces an unwilling accomplice to help him search for Katherine, leading to a confusing and life-threatening situation for Matt. Finally, Silas reveals the reason he's determined to find Katherine, and Damon and Elena face a disturbing new reality.

Damon and Elena are skeptical of Silas's new goal; Tessa realizes she was outsmarted by Silas; after discovering a new consequence of becoming human, Katherine decides she needs a new place to stay; Bonnie is impressed with Jeremy.

The power of doppelgangers.... While Elena and Damon try to explain Amara's situation to Stefan, Dr. Wes Maxfield gives Katherine some deeply disturbing news. Nadia shows up at Caroline's dorm room searching for Katherine. After a surprising conversation with Amara, Jeremy and Bonnie share a glimmer of hope. Silas fails to keep a promise, causing Damon to turn to Tessa for help with his new plan, and Stefan makes a heartbreaking confession to Damon and Elena.

Back to Katherine's early life 1490, Nadia helps her mom with a fighting plan.

Damon tries to get back together with Elena, however, Katherine has a plan and attempts to take Elena's body permanently. Tyler is upset with Caroline and Matt is used by Katherine. Enzo finds Damon and they decide to become a team again.

While Nadia remembers her centuries-long search for her mother, Stefan, Caroline and Matt come up with a desperate new plan to save Elena's life. For the second time, Bonnie and Jeremy must turn to Liv for help. Damon baits Tyler into a nasty confrontation, then takes off to seek revenge on Dr. Wes. Caroline and Tyler come to a new understanding. Finally, Bonnie learns of a terrifying secret that will threaten the lives of all her friends.

With the fate of Mystic Falls at stake, Stefan and Damon must fight their greatest enemy for one last battle.