Robin investigates when she thinks Barney is cheating on her, only to find that he is spending his time with Ted, taking lessons in how to date her.
McGarrett and Five-0 search for a Russian spy who throws the life of one of their own into jeopardy when he steals NSA secrets.
After spending a passionate summer with Damon and ensuring that Jeremy is adjusting to his return from the dead, Elena moves into Whitmore College with Caroline; a student named Megan shows up in Bonnie's place at the dorm.
Damon asks Matt and Jeremy to keep Elena's doppelganger, Katherine, out of sight while Silas searches for her, but the situation quickly spirals out of control.
Katherine and Elena have the same dream about Stefan being in danger and talk Damon into helping them look for him; Matt winds up in a confusing and life-threatening situation.