4x05  The Killer: THE HUNTER’S MARK — Stefan and Klaus form an uneasy alliance to try and contain the danger that Connor (guest star Todd Williams) has unleashed on the town. When Connor takes Jeremy, Matt and April (guest star Grace Phipps) hostage at the Grill, Stefan and Damon have a serious disagreement about the best course of action, and Elena is again caught between the two brothers. The situation quickly turns violent when Klaus sends one of his hybrids, Dean (guest star Blake Hood, “The Young and the Restless”) to stand up to Connor. Caroline is surprised to find Hayley (guest star Phoebe Tonkin) at the Lockwood mansion. Meanwhile, Professor Shane (guest star David Alpay) works with Bonnie to help her get past her fear and guilt. 4x06  We All Go A Little Mad Sometimes: ELENA’S NEW NIGHTMARE- Terrifying hallucinations leave Elena (Nina Dobrev) shaken and confused, causing her to make a dangerous mistake. After giving Stefan (Paul Wesley) some very disturbing news about Elena, Klaus (Joseph Morgan) takes matters into his own hands. Professor Shane (guest star David Alpay) reveals a story of ancient witchcraft to Damon (Ian Somerhalder) and Bonnie (Kat Graham). With help from Klaus and Stefan, Jeremy (Steven R. McQueen) begins a new chapter in his life. Finally, Elena makes a painful personal confession to Stefan, and Matt (Zach Roerig) gives Damon startling new information about Professor Shane.