Robin and Barney make their relationship official but Barney is finding it hard to adjust from being a bachelor to having a relationship. Robin worries whether Barney is capable of being in a relationship and Ted overhears and tells Barney. Will Barney try harder in his relationship?
Katherine recalls the traumatic night in 1490 when she gave birth to a daughter who was taken from her. Nadia creates a frightening plan to protect her mother. Caroline forgets to fill Elena in on the latest gossip, then indulges in some scandalous behaviour of her own.
Elena and Katherine both dream that Stefan is in danger and convince Damon to help them find him. But their plans are thwarted by a mysterious woman who seems to know everything about Stefan's past and Damon's disturbing future.
At Whitmore College, Elena and Caroline decide it's time to throw a big party, but their plans are interrupted when Jesse suddenly needs Caroline's help. Meanwhile, Damon makes a terrifying discovery about a secret society.
Damon is forced to deal with a part of his past he thought was gone forever when Dr. Wes unleashes a secret weapon to stop him from saving Elena. Meanwhile, Elena is horrified by Dr. Wes' confessions about the dark history of Whitmore College and his own ultimate goal.