Following a mysterious disappearance, Serena Van der Woodsen suddenly returns to the Upper East Side from boarding school to visit her suicidal brother, Eric. Shock spreads across the Upper East Side as the first sightings of her spread across the Gossip Girl website. Blair Waldorf soon discovers Serena had slept with her boyfriend, Nate Archibald, the night of her disappearance. Meanwhile, Brooklynite Dan Humphrey and Serena begin dating while Nate struggles with his feelings for Blair. Nate and Blair try to salvage their relationship, driving Blair to lose her virginity to Nate's best friend, Chuck Bass. Jenny Humphrey, Dan's sister, is trying to fit in to the Upper East Side by following around Blair and her friends. Vanessa Abrams, Dan's best friend, returns. It is revealed that Dan had confessed his love for Vanessa in the past, but the two move beyond this as friends. It is discovered that Lily Van der Woodsen, Serena's mother, and Rufus Humphrey, Dan's father, have a romantic past and begin to rekindle their romance. The two decide to see other people in light of their children's romance. Blair and Nate eventually break up, after finally having sex, despite her affair with Chuck. Nate discovers the affair, causing a rift with Chuck. Throughout the season, Chuck tries to seduce Blair and the two somewhat come to terms with their feelings for each other. Georgina Sparks, past friend of Serena, returns and causes havoc, including outing Eric Van der Woodsen as gay. Georgina's return reminds Serena of the real reason she left the Upper East Side. Problems erupt between Dan and Serena, as Serena tries to hide her secret from him. Georgina pretends to be a woman named Sarah from Portland and befriends Dan and Vanessa. It is revealed that Serena left the Upper East Side because she was involved in a drug-related death and felt responsible for the situation. However, the incident is resolved with Serena being absolved of her guilt and Georgina leaves. Dan and Serena decide to end their relationship. Meanwhile, Lily accepts a marriage proposal from Bart Bass, despite her feelings for Rufus, and the season ends with a Bass wedding and Blair waiting for Chuck at the airport.