In the Season 4 opener, Blair and Serena enjoy summer in Paris, trying to forget about the guys back home. Elsewhere, Nate meets a woman (Katie Cassidy) who disapproves of his playboy behavior; and Dan plays house with Georgina and her newborn baby.
Lily asks Serena to track down Chuck, who has found a new life and a new love interest in Europe. Meanwhile, Blair gets a second chance with Louis; and Juliet devises a plan to help Nate win back Serena, though it involves manipulating Dan and Vanessa.
Blair begins her studies at Columbia and seeks entry into a prestigious social club. Elsewhere, Serena develops a distrust of Juliet, who she suspects is deliberately wreaking havoc on her life; and Rufus' concerns about Dan compel him to take action.
A suspicious Nate asks Juliet what she's hiding from him. Elsewhere, Blair plots to put an end to Chuck's current state of bliss; and Dan is once again conflicted about his feelings for both Serena and Vanessa.
Blair enrolls in a class taught by a savvy businesswoman and tries to become her assistant, but another student sabotages this plan. Meanwhile, a hurtful rumor about Serena is posted anonymously on Gossip Girl.
Chuck throws a masquerade party at his hotel, where Serena behaves erratically and baffles Dan and Nate. Meanwhile, Blair tries to impress Anne Archibald so she can get involved in her foundation, but Blair's association with Chuck works against her.
Bart Bass' former associate (Michael Boatman) arrives in town with his daughter (Tika Sumpter). Meanwhile, Chuck and Serena team up to oppose Lily; Blair begins to view her mother as an asset to her future career; and Nate worries about his father, who's now out on parole.
Blair needs Nate's help to score points with her boss. Elsewhere, Damien causes turmoil; and Chuck struggles to draw a line between his personal and professional life. Florence and the Machine perform.
Lily's mother, sister and ex-husband arrive to support her and take part in a photo shoot celebrating their family. Then Lily's niece shows up unexpectedly, seeing the Upper East Side for the first time. Meanwhile, Blair has a revelation about her future and struggles with what she believes is her destiny.
Blair gets a shot at happiness---until Serena threatens to shoot it down by bringing up the past. Meanwhile, a questionable friendship develops between Charlie and Vanessa; and as Nate's romance with Raina grows, he struggles to keep a secret for Chuck.
Uncle Jack returns to town and causes problems for Chuck. Meanwhile, Blair feels conflicted about her many suitors; and Charlie's newfound comfort with the Upper East Side is shaken at a charity event.
In the fourth-season finale, Blair has a difficult choice to make concerning her love life. Meanwhile, a bored Georgina resurfaces; Serena searches for Charlie; and Vanessa stumbles across a manuscript Dan wrote. "Gossip Girl" author Cecily von Ziegesar makes a cameo appearance; and Airborne Toxic Event perform.