The privileged prep school teens on Manhattan's Upper East Side first learn that Serena van der Woodsen (Blake Lively, "The Sisterhood of the Traveling Pants") is back in town the way they learn all the important news in their lives -- from the blog of the all-knowing albeit ultra- secretive Gossip Girl. No one knows Gossip Girl's identity, but everyone in this exclusive and complicated vicious circle relies on her website and text messages for the latest scoop. Even Serena's closest friend, Blair Waldorf (Leighton Meester, "Entourage"), is surprised to find that Serena has suddenly ended her self-imposed exile to boarding school and returned to Manhattan. Once the Upper East Side's most notorious party girl, Serena's reasons for returning are mysterious, although they may have something to do with her younger brother Eric (Connor Paolo, "Alexander"). Whatever the reasons, the change in Serena is obvious, especially to Blair, whose friendship with Serena has always been competitive and difficult.

In the wake of the scandalous Kiss on the Lips party, Serena receives an ice-cold reception from her best friend, Blair, who reveals that she knows Serena slept with her boyfriend, Nate, before mysteriously running off to boarding school. Serena decides to take Dan to archenemy Chuck's fundraiser brunch at The Palace. And Jenny seeks advice from Blair, who realizes she may have something to gain by allowing Jenny into her inner circle.

As the Upper East Side teens from Constance Billard and St. Jude's prepare for a much-anticipated visit from Ivy League representatives, Blair uncovers scandalous information about Serena that may not remain a secret much longer. Dan has his heart -- and future -- set on serving in the coveted usher position for the Dartmouth representative. But he is beat out by Nate, who has no interest in the school, despite pressure from his controlling father, the Captain (recurring guest star SAM ROBARDS). Meanwhile, Jenny bonds with Serena's younger brother, Eric (recurring guest star CONNOR PAOLO). And Rufus must swallow his pride and ask Lily for a favor to help his son, Dan.

Blair is thrilled when her mother chooses her to be the new face of her clothing line. However, Blair's happiness soon turns to feelings of betrayal and jealousy when Serena moves into the spotlight, and Blair finds herself back in Serena's shadow. Meanwhile, Serena and Dan are reminded once again that they come from two very different worlds. And Nate and Chuck indulge in a boys' weekend to blow off steam after Ivy Week.

Serena and Dan go on their first date; Lily discovers that Eric is missing from the treatment center.

Dan is torn between two girls when his childhood friend, Vanessa (recurring guest star JESSICA SZOHR), returns home and declares her feelings for him, just as he and Serena are trying to figure out what they mean to each other. At her infamous masked ball, Blair sends Nate on a scavenger hunt, but he is still distracted by his feelings for Serena. Although Blair makes it perfectly clear that outsiders are not welcome, a disguised Jenny and Dan sneak into the ball. Meanwhile, Lily asks Rufus to accompany her to an event hosted by Blair's mother in order to make Chuck's father, who brought a model ("America's Next Top Model" winner CARIDEE ENGLISH) as his date, jealous.