A KILLER VIRUS — When Stefan tries to explain recent events to a very sick Elena, her first instinct is to call Damon. At the same time, Damon is trying to figure out how to make a disturbing confession to Elena. While going through Dr. Wes’ files, Caroline discovers a frightening secret, and is surprised when Enzo (guest star Michael Malarkey) appears, claiming to have the solution everyone is searching for. At Enzo’s insistence, Caroline asks Stefan to meet her at a mysterious location where they are joined by a group of Travelers, including Sloan (guest star Caitlin McHugh), who reveals new information on the importance of doppelgangers. During spring break on a mostly deserted Whitmore campus, Elena runs into Luke (guest star Chris Brochu), a student who seems to know her, though she has no memory of meeting him. Recently dumped by his boyfriend, Luke proposes that he and Elena spend the break getting drunk together, but she sends him off on an urgent mission to find Bonnie and the “newbie” witch, Liv (guest star Penelope Mitchell). Damon finally tells Elena the truth about his recent activities, and they come to a new agreement about their relationship. Pascal Verschooris directed the episode written by Caroline Dries.