when do they find out that katherine is in elena's body
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.
Lindsay Monroe In episode 9.13 ("Nine Thirteen") Lindsay reveals to Danny that she is pregnant with their second child.
Emily Prentiss Brewster returned for guest appearances in the season 9 episode "200" in 2014 and the season 11 episode "Tribute" in early 2016 before returning as a regular cast member in the season 12 episode "Taboo" later in the year.[18]
Are You the One? In Episode 10, the cast did not find all their perfect matches, winning no money at the end.