S5, E10: Damon realizes Elena is in danger and enlists Stefan’s help to find her. The brothers pay a visit to Aaron (recurring guest star Shaun Sipos), and Damon shocks Stefan by revealing his first-hand knowledge of Aaron’s family. In an attempt to stop Damon, Dr. Wes (recurring guest star Rick Cosnett) unleashes his secret weapon, forcing Damon to deal with a part of his past he thought was gone forever, as well as the consequences of his decades-long plan for revenge. Meanwhile, Elena is horrified by Dr. Wes’ confessions about the dark history of Whitmore College and his own ultimate goal. Finally, a frantic Katherine turns to Matt for help, until she realizes that Nadia (recurring guest star Olga Fonda) may be the one who can solve her problem.