Impromptu party at the school swimming pool!!! 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.