when do they find out that katherine is inside elena
No Exit (The Vampire Diaries) Damon wakes up chained on the Salvatore house's basement. Stefan is there and Damon tries to warn him that because of his cravings, one day he will kill him but Stefan tells him that they will find a solution. Damon points to Stefan that "Elena" provoked him to feed on her and then she kicked a stake towards him so he will kill him. Stefan does not believe that Elena would want that, he locks Damon up and gets upstairs where Caroline is. The two of them discuss what happened between Stefan and "Elena" and Caroline also tells him about Nadia and Matt and the text he sent to her. From Matt's text, who used "K" and not "E", they put the pieces together and they realize that Katherine is in Elena's body.
Marcus Álvarez
Damon Salvatore In season two, Katherine tells Damon that she never loved him and that it was always Stefan. Elena says something similar later, leaving Damon heartbroken. As an expression of his anger, pain, and hopelessness, he snaps Jeremy Gilbert's neck, not realizing he is wearing a ring which reverses damage done by supernatural creatures or forces. Jeremy survives because of the ring, but Damon's action incurs Elena's wrath and pain. When Bonnie also discovers it was his blood that enabled Caroline Forbes to become a vampire, the two declare their hatred for him, leaving angrier than ever.[7] After saving Elena with Stefan in episode 8 of season 2, Damon shows up in Elena's room with the vervain necklace that was ripped from her neck earlier in the episode. Before he gives it back, he tells Elena that he is in love with her, and because he is in love with her, he cannot be selfish with her. He also states that he doesn't deserve her, but that his brother does. He kisses her forehead and says he wishes she could remember this, but she can't. As the camera shows a close up of Damon's eye as he is compelling Elena to forget, a tear slips. Elena blinks and her vervain necklace is back around her neck, Damon is gone and her window is open with the curtains blowing. She had no recollection as to how the necklace was returned to her. In one episode, Damon joins Rose to find out why the originals are after Elena; after some time and clever banter, the two have sex, stating that they could rid themselves of emotion. However, when Rose, Damon's old friend who turned Katerina, suffers from a werewolf bite, he gives her the memory of her life prior to becoming a vampire, and helps her remember how good it felt to be able to wall and feel the sunlight, without it burning her. During this meaningful moment, Damon mercifully kills her, leaving him to mourn the death of his one of very few friends. Elena and Damon then begin to mend fences, and Elena gives him an affectionate hug to help comfort him after Rose's death. Damon begins showing another side of himself in small acts that help build what once was an impossible friendship between Elena and himself, after she clearly stated that he has lost her forever. After he spares Caroline's mother, Elena says how that was the person she was once friends with. And it's hard for Damon to accept that he has to change to have her in his life, which he explains to Andy Star, his compelled girlfriend a few more episodes in. Damon is bitten by Tyler the werewolf at the end of the season. Elena takes care of him, and right before he is cured by the blood of Klaus, the original hybrid, she gives him a "goodbye" kiss, because she was sure he was going to die. She even forgives him, telling him that she cares for him through grief-stricken tears.
List of St. Elsewhere characters Portrayed by Denzel Washington