When Lily’s ex-husband, Dr. William van der Woodsen, shows up unexpectedly in Manhattan, Serena finally gets the reunion she has so desperately wanted with her father, but the circumstances turn out to be far from ideal. When Serena and Nate continue to have relationship issues, a scheming Jenny is more than happy to be a shoulder for Nate to lean on... Meanwhile, Dan finds out that he didn’t get accepted into the Tisch writing program and Vanessa admits she may have been somewhat responsible.

Will's return to the Upper East Side continues to stir up problems for Serena, Lily and his long-standing rival, Rufus. Serena and Jenny's relationship is strained as a result of Jenny's deception. Blair spends time on the Columbia campus and realizes where she truly belongs.... Dan learns that Vanessa has been keeping yet another secret from him.

When things get tense between Rufus and Will, Serena chooses to stand behind her father, while at the Rufus is made to feel like an outsider in his own family. Meanwhile, Jenny deliberately shares information with Will that may ultimately destroy Lily and Rufus' marriage. After many failed attempts, Chuck makes one last grand gesture to reconcile with Blair, hoping she will finally accept the fact that they are destined to be together.

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.

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.

Blair thinks Cyrus may have found a potential loophole in her prenup. Chuck and Georgina partner up in a scheme, but it has an unpredictable outcome.. Meanwhile, a family crisis brings William van der Woodsen back to the Upper East Side.

Chuck invites Jack to town to thank him for saving his life, but finds the trip doesn’t go exactly as planned. Blair and Dan attempt to consummate their new relationship -- but unexpected roadblocks get in their way. Meanwhile, Ivy finds an unlikely ally in William in her quest to be accepted on the Upper East Side, and Nate is hopeful a new investor will save his newspaper.

Blair feels like her Upper East Side status might be slipping away and devises a plan to assure that doesn’t happen. Meanwhile, Lily throws a family gathering – including William, Carol and Lola – in an attempt to prove the van der Woodsen family is as united as ever. Finally, Nate digs into Diana’s past and is surprised by what he discovers.

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?

Serena and Dan realize that they need to make amends with the people they have wronged. Chuck’s search for evidence of his father’s illegal activities leads him to a showdown with Bart.

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.