Stefan and Damon decide on a new plan to deal with Katherine at the masquerade ball.

Damon, Alaric and Elena reach a hidden cage in the secret tunnel beneath the Lockwood mansion. Alaric studies the runes and primitive pictures, which indicate it was the home of an ancient Viking family, who interacted with the Original werewolf, vampires and witch. They confront Rebekah, who is shocked to tie it up with her memories of her family's youth, when their father Mikael, now the only hunter they truly dread, bullied his sons, especially Niklaus, leading in interaction with the originally friendly werewolf neighbors to family drama and the origin of vampires. After taunting Stefan, Damon releases him from Lexi's 'aversion therapy' and takes him along to seek Mikael's help. Alaric and Elena work out that Rebekah's memories don't take account of a last, crucial cruel twist.

The homecoming dance becomes the backdrop for a battle of lethal wits between Damon's party, including Mikael and Rebekah although not at all reconciled, and Klaus's, which fields the hybrids by diverting the party to the Lockwood mansion. Tyler surprises Caroline by stating he doesn't really mind being under Klaus's spell as hybrid, it's not worse than monthly lunatic agony as pure werewolf. Fearing even with the eternal oak stake in Mikael's hand Klaus may outsmart them, Damon secretly enlisted Katherine, but Klaus prepared the most stunning surprise.

The 1920s Decade Dance takes a deadly turn when Damon and Stefan realize they need the help of Matt, Jeremy and Bonnie to undo a spell that could be devastating for everyone.