After a brief encounter abroad, Chuck (Ed Westwick) and Blair (Leighton Meester) make a promise to each other about their relationship, which leaves them once again apart. Dan (Penn Badgley), with some help from an unlikely ally, Georgina (guest star Michelle Trachtenberg), is writing a scathing tell-all book that can only mean trouble. As the sole head of The Spectator, Nate (Chace Crawford) is making his own decisions and is ready to go up against Gossip Girl. As word spreads that Serena (Blake Lively) is missing, the gang bands together to find her and are shocked by what they find. Kelly Rutherford, Matthew Settle and Kaylee DeFer also star. Robert John Burke and Sofia Black-D’Elia (“Skins”) guest star.