Serena throws Jenny a sixteenth birthday party, but things spin out of control when Poppy Lifton turns the party into the social event of the season. Vanessa agrees to help Chuck in a plan concerning Blair and Nate. Meanwhile, Rufus searches for a way to cover Dan's tuition when he learns he will not receive financial aid to go to Yale.

As summer draws to an end, Blair and Chuck continue to adjust to being in a relationship with one another. Serena returns from Europe with new secrets to hide and a new relationship with Carter Baizen. Nate also returns from vacationing and brings home a mysterious girl, Bree Buckley. Meanwhile, Rufus, Dan and Jenny spend the summer in the Hamptons and learn to adjust to the van der Woodsen's glamorous lifestyle

Lily and Rufus decide to move up their wedding to the next day, but will someone or something come between them before they become man and wife? Chuck discovers a secret that Carter has been keeping from Serena. Dan and Vanessa are pulled into one of Georgina’s schemes. Blair is suspect of Bree and shares her concerns with Nate.

In need of publicity for his new hotel, Chuck decides to move up his club’s opening and enlists Serena’s help to get the word out to her celebrity clients. Feeling left out of the planning, Blair attempts to win Chuck’s approval by secretly helping him with a problem concerning opening night. Dan is unnerved when he finally watches one of Olivia’s infamous sex scenes with co-star and real-life boyfriend at the time, Patrick Robinson. Jenny is forced to choose between her relationship with Eric and her new role as Queen Bee. Rufus gets Lily into the Halloween spirit.

It wouldn’t be Thanksgiving on the Upper East Side if there wasn’t a serving or two of some major drama for the holiday. Blair suspects her mom has been keeping a big secret from her, but it turns out to be something else entirely. Vanessa is supposed to spend Thanksgiving with her parents, but has a fight with her mom and shows up on Dan’s doorstep. Rufus learns that Lily has been lying to him about her mother, Cece. Chuck tells Nate that he has some potentially damaging information about one of their friends. Jenny learns that Eric was behind her very public embarrassment at Cotillion and can’t pass up a chance to get even. Serena is put in a very awkward position when her mother invites Trip and Maureen to join them for Thanksgiving dinner.

Rufus and Lily grow suspect of Jenny’s relationship with Damien. Chuck learns more about the woman who may or may not be his mother. Dan and Vanessa struggle through the awkwardness of dating other people.

Chuck and Blair are faced with the most difficult decision they have ever faced as a couple. Serena plans a surprise birthday party for Nate, but Jenny does her best to sabotage Serenas’s efforts. Dan and Vanessa’s new relationship hits a bump in the road.

Chuck offers to throw a wedding for a very pregnant Dorota who insists that she and Vanya have a traditional wedding before her parents arrive from Poland and find their daughter pregnant and without a husband.. Dorota asks Blair and Chuck to be part of the ceremony and walk her down the aisle. Serena tells Nate she is having breakfast with the Humphreys when in reality she’s secretly meeting up with Carter Baizen. Rufus discovers that Lily has been lying to him about her whereabouts.

Blair must decide whether to meet Chuck at the top of the Empire State Building or risk losing their future together. A Gossip Girl gossip bomb involving Dan explodes Serena and Nate's relationship. Dorota and Vanya welcome their baby. Jenny hits rock bottom. Georgina returns to the Upper East Side...and she has an agenda.

Although Blair made it perfectly clear that Little J was no longer welcome in Manhattan after what happened with Chuck, Jenny is tempted by a once-in-a-lifetime opportunity to meet Tim Gunn, which could be a game changer for her future. Meanwhile, Serena discovers something about her new boyfriend, Colin, that may put an end to their relationship just as it was getting good.

Ben’s mother comes to town, forcing issues to the surface between Ben and Serena. Russell Thorpe is determined to destroy Chuck’s family legacy, but he risks alienating his daughter, Raina, in the process. Billy Baldwin returns as William van der Woodsen, Lily’s ex-husband and Serena and Eric’s father.

Serena decides she is ready to relinquish the spotlight and sets out to make a reluctant Lola the next “It Girl” of the Upper East Side, starting with modeling at a Kiki de Montparnasse lingerie show. Meanwhile, Chuck reaches out to Blair or advice about his past, and Diana Payne’s return to The Spectator starts a power struggle with Nate.

To celebrate their official coming out as a couple, Blair and Dan host a glamorous British-themed Salon, including guests Julian Tepper and Jenna Gribbon Lola lands the audition of a lifetime, but Gossip Girl may have other plans for the Upper East Side’s latest It Girl. Meanwhile, Lily and Rufus disagree over the best way to handle the Ivy situation, and Serena and Diana face-off over secrets they both would prefer remain secrets.

When Gossip Girl goes after Blair as she’s never done before, Serena admits she may have unintentionally played an important role in Blair’s latest nightmare. Meanwhile, Nate invites Lola to move in with him, and Lily must make a big decision about the future of her marriage. Finally, by episode’s end, Blair will make a choice between the two men in her life…will it be Chuck or will it be Dan?

After a brief encounter abroad, Chuck and Blair make a promise to each other about their relationship, which leaves them once again apart. Dan, with some help from an unlikely ally, Georgina, is writing a scathing tell-all book that can only mean trouble. As the sole head of The Spectator, Nate is making his own decisions and is ready to go up against Gossip Girl. As word spreads that Serena is missing, the gang bands together to find her and are shocked by what they find.