The Grandfather (S02E19)

Devastated by the recent plot twist in her life, Blair turns her back on her predictable Waldorf existence in favor of a wilder lifestyle, causing Serena and Chuck to have serious concerns about their friend. Vanessa convinces Nate that it may be time to forgive and forget when it comes to the Vanderbilts, his mother's Kennedyesque family, who abandoned Nate and his mother when they needed them most. Plus, in a misguided effort to be completely honest with each other, Lily and Rufus agree to share lists of their past lovers. (Warner Bros. UK)