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. 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.