Chuck and Blair make a promise to each other. Dan enlists Georgina to write a tell-all book. Nate decides to have The Spectator go after Gossip Girl. The gang is stunned at what their search for Serena turns up.

Serena hosts a gala to prove herself in adult society. A rival may impact the release of Blair's fashion line. Dan must weigh personal integrity versus getting published. Chuck presses Amira to help him investigate his father's past.

Blair must rely on help from an unlikely source. Serena discovers that befriending Sage is trickier than she thought. Nate publishes Dan’s first article. Chuck begins to uncover what Bart is hiding.

Chuck’s investigation leads him to an event where he hopes to find the one person who can tell him the truth about Bart. Serena and Steven decide to reveal their romantic histories. Nate must make a difficult decision in order to keep The Spectator in business.

Eleanor gives Blair an ultimatum. Serena becomes worried about Steven’s attitude toward her. Chuck finds an unlikely ally as he tries to expose his father’s secret. Dan publishes another article.

Blair gets ready for her mothers imminent arrival. Serena volunteers to help Dan find a new place to live. Ivy, Chuck and Nate try to retrieve incriminating evidence on Chuck's father. Rufus and Ivy must scramble to make their gallery opening a success.

Serena and Dan try make amends with the people they have wronged. Blair has one last chance to prove to her mother her worth as a fashion designer. Chuck is close to getting the evidence he needs against his father.

Serena and Dan decide to throw their first Thanksgiving together. Chuck begins a downward spiral, leaving Blair to find a solution to his problems. Dan must make a tough decision whether to publish a potentially friendship-destroying expose.

Blair grows alarmingly concerned for Chuck’s safety and devises a plan with Serena, Georgina and Sage. Chuck makes a deal that could change his life. Nate's financial dilemma finally lands him in a place that he never thought he would be.

In a fashionable farewell to remember, our favorite Upper East Siders join forces for one last soiree, and the shocking identity of Gossip Girl is finally revealed.