Season 1 Episode 13

Gossip Girl reports that Serena van der Woodsen was seen buying a pregnancy test. Of course, on the Upper East Side, the truth is often even juicier and more scandalous than the gossip. Nate finds out about Blair's and Chuck's affair (Source: TV.com).

Season 1 Episode 12

Serena, Blair, Nate, Chuck and their class break into the school swimming pool for a night of fun, but when someone nearly dies, the school threatens to expel the person responsible for the break-in. Everyone agrees to not say anything, but this creates major problems between Serena and Dan, because Dan is not ready to take the fall for someone else and risk his future. Vanessa, while working on a documentary project about private schools, accidentally captures Blair and Chuck discussing their affair. Lily tries to tell Rufus how she really feels about him (Source: TV.com).

Season 1 Episode 11

Blair's father comes home for the holidays with an unexpected guest, his boyfriend Roman. Blair cannot hide her disappointment and makes a plan to get rid of Roman. Jenny and Vanessa help Serena get the best Christmas present ever for Dan, who has a surprise of his own for Serena. When Chuck texts Blair that Nate is with him in Monaco, Blair worries that Chuck may tell Nate about their hook-up. Rufus refuses to remain the understanding husband after Alison's former lover calls the house (Source: TV.com).

Season 1 Episode 10

Serena had no intention of attending the upcoming Debutante Ball, until her grandmother CeCe announces that she must. Cece does not approve of Dan as Serena's escort, causing a rift between Serena and Dan. Although they are officially broken up, Nate asks Blair to go to the ball with him. She accepts, but only as friends. However, a jealous Nate begins to suspect that Blair is seeing someone else. Jenny finds herself with the decision of either attending her mother's art opening or following her dreams to the Debutante Ball, even though her parents don't want her to go (Source: TV.com).

Season 1 Episode 9

Dan invites Serena and her family to spend the holiday with his family, creating an uncomfortable situation for Rufus and Lily. The children are unaware of their parents' complicated romantic past. Meanwhile, Blair freaks out when she learns that her father isn't coming home for Thanksgiving. Nate spends the holiday with his family, but their awkward dinner quickly goes from bad to worse (Source: TV.com).