The Vampire Diaries is adapted from the best-selling series of novels of the same name by American female writer LJ Smith. The relationships between the characters in this season are more complicated, and various characters appear one after another. The return of Kathrine (Nina Dobrev) makes the relationship between Elena (Nina Dobrev), Stefan (Paul Wesley) and Damen (Ian Somerhalder) more complicated. Elena not only knows that her uncle John is her biological father, but also finds out that Alaric's long-lost wife Isobel is her biological mother. Tyler also discovers the secret of his family-turning into a werewolf on a full moon night. Elena, the elder vampire who Kathrine has been hiding for hundreds of years, suddenly appears, and everyone's target is the mixed-blood vampire klaus. Klaus' ultimate goal is to kill Elena and get the blood of the double body. Everything will develop in an inevitable direction...