S4, E9: As a Winter Wonderland–themed party fills the streets of Mystic Falls, Stefan and Caroline find themselves at odds with Tyler over his plans for Klaus and his hybrids. When Caroline proposes a solution to their problem, Hayley (recurring guest star Phoebe Tonkin) finds a dramatic way to make it clear that she is not on board. Later, Klaus makes a discovery that leads to chaos and violence. Meanwhile, Elena and Damon retreat to the Gilbert lake house to help Jeremy conquer some dangerous inner demons with the help of Bonnie and Professor Shane (recurring guest star David Alpay), who reveals a piece of ancient history that leaves them all speechless.