Jenny’s kinda-not-sweet sixteen! Serena throws Jenny a small birthday party for her sweet sixteenth, but things get out of control when Poppy Lifton turns the birthday into a huge social event. Vanessa, in a moment of desperation, agrees to help Chuck with a scheme having to do with Blair and Nate. Meanwhile, Rufus tries to figure out how to cover Dan’s Yale tuition, when he learns that Dan will not receive financial aid.

Serena invites Aaron to be her guest at a charity gala honoring Lily and Bart, but after discovering a secret that Aaron has been keeping from her she begins to question whether Aaron is the guy she thought he was. Hoping it will help her chances of getting into Yale, Blair naively agrees to babysit the 15-year-old daughter of a prominent Yale donor, but the teenager proves to be more than a handful and Blair begins to suspect that the evening may actually wind up hurting her chances of getting into the college of her dreams. Meanwhile, Jenny and Agnes plan a guerilla fashion show that will either launch Jenny’s stardom or ruin her chances of ever being accepted by the industry.

Blair is against the idea of her mother with Cyrus Rose a new man in her life and does whatever she can to sabotage their relationship. Jenny moves in with Agnes and tries to secure a business deal, but Agnes doesn’t want to put in the effort. Serena and Aaron fall for each other but something about Aaron threatens to ruin their new relationship. Dan and Chuck are at war due to Dan’s true interest in his father Bart Bass. Dan has to decide whether to submit the Chuck Bass story or protect the Bass family from scandal. Blair’s 18th birthday is also addressed.