As 'Gossip Girl' posts news of the annual Cotillion Ball to take place on the approaching weekend, Blair decides not to go with Nate, but she finds herself being featured in The New York Times and is enjoying her secret affair with Chuck. Serena decides not to go either, so her grandmother, CeCe, shows up to change her mind. Meanwhile, Jenny volunteers for the ball and Lily takes her under her wing. But the night of The Cotillion is the night of Alison's first art opening, and Rufus and Alison tell Jenny that she cannot attend the ball. Jenny decides to defy them both by secretly attending the dance anyway. Refreshed by Blair's newly buoyant attitude, Nate asks her to the Cotillion and she accepts, which makes Chuck jealous. CeCe tells Lily and Serena that she is sick with lung cancer and her last dying wish is to see Serena go to the ball, and she wants Serena to go with the wealthy Carter Baizen. The snobbish CeCe takes an instant dislike to Dan and she approaches Rufus with an offer pay him to convince Dan not to go with Serena. Dan learns of this and tells Serena that he does not think very highly of CeCe by telling Serena about how CeCe tried to bribe his father to persuade him not to attend. Surprisingly, the skeptic Serena refuses to believe Dan that her compassionate grandmother is a crafty snob, and she ends up going to the ball with Carter... both her and Dan having fallen right into CeCe's ploy. Also, Chuck manipulates Nate into thinking Carter is having an affair with Blair to provoke a fight with him.

Gossip Girl heads to the Hamptons as summer comes to a close; Serena and Nate fake a relationship as a cover for Nate's affair with a married woman.

A sudden and tragic event impacts the lives of everyone on the Upper East Side, especially Chuck and the van der Woodsens.

To prove her independence, Serena refuses to leave jail with her mother or her grandmother; Rufus is furious with Lily for having Serena arrested.

Serena is put in an awkward position when Lily invites Tripp and Maureen to join them for dinner; Blair suspects her mother of keeping a big secret; Jenny gets even with Eric in the most cruel way.

Despite being grounded, Jenny continues to see Damien who tells Jenny that he wants to have sex with her. Lily thinks to tell the secret that she has up till now concealed, but after a call, she changes her mind. Dan and Vanessa explore the new development in their friendship. Chuck is forced to make an extremely difficult decision about his hotel. Meanwhile, Serena and Nate have a fight that is reminiscent of past events.

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.

As Lily awaits the consequences of her decision, William van der Woodsen, CeCe and Lily's sister, Carol, come into town to support her and be part of a Taschen photo shoot on "modern royalty" in which the Rhodes family is participating. Unbeknownst to Carol, who has always chosen to keep her daughter Charlie far away from the Upper East Side, Charlie has followed her to New York to meet Serena and the rest of the family. Blair has an epiphany about her future, and grapples with the knowledge of whom she's destined to be with.

Lily, Charlie and Serena eagerly anticipate the Studio 54 party being thrown in CeCe's honor. Nate takes on a new role at the Spectator, but his first big story turns out to be about someone he knows all too well.

Dan feels honored when he learns that Upright Citizen's Brigade is performing excerpts from his book, Inside. Blair tries to prove Serena's suspicions wrong in order to save their friendship. On her way out of town, Ivy ends up on a collision course with the van der Woodsens.