Stefan and Damon are furious when they discover that Elena has defied them both to make a new ally and take control of the plan to out-maneuver Klaus (recurring guest star JOSEPH MORGAN -- Ben Hur, Doc Martin). Disagreement over how to protect Elena leads to growing tension between the Salvatore brothers. Meanwhile, Stefan has his hands full trying to keep a confused and frightened Jenna safe. Flashbacks to 1491 reveal Katherine's introduction to Elijah (recurring guest star DANIEL GILLIES) and Klaus, along with the origin of the moonstone curse. Plus, Elena learns shocking new information about Klaus' motives.