20. It's a Dad, Dad, Dad, Dad World

Complete story — includes the ending

Will's return to the Upper East Side continues to stir up problems for Serena, Lily, and his long-standing rival, Rufus. Meanwhile, Serena and Jenny's relationship is strained as a result of Jenny's deception over Nate. Blair spends time on the Columbia University campus and realizes where she truly belongs. Dan learns that Vanessa has been keeping yet another secret from him when she informs him that she has decided to leave town for more international activist work in Haiti. Elsewhere, Chuck struggles with the idea of Lily's sickness while he continues to try to make up with Blair. Title reference: The 1964 film It's a Mad, Mad, Mad World.