S6, E1: In the sixth season premiere, after a brief encounter abroad, Chuck and Blair make a promise to each other about their relationship … which leaves them once again apart. Dan, with some help from an unlikely ally, Georgina Sparks (recurring guest star MICHELLE TRACHTENBERG), is writing a scathing tell-all book that can only mean trouble. Meanwhile, as the sole head of The Spectator, Nate is making his own decisions and is ready to go up against Gossip Girl. As word spreads that Serena is missing, the gang bands together to find her and are shocked by what they find. Recurring guest stars also include BARRY WATSON (7th Heaven, Samantha Who?) as Steven, ANDREA GABRIEL (Lost) as Amira, ROBERT JOHN BURKE (Person of Interest, Rescue Me) as Bart Bass and SOFIA BLACK-D'ELIA (Skins) as Sage.