Chuck hosts a "Saints and Sinners" masquerade party at the Empire Hotel. At the party, Dan and Nate don't know what to make of Serena's strange behavior and mixed messages. Blair sets her sights on becoming the new face of Anne Archibald's foundation for girls, but Anne is concerned that Blair's friendship with Chuck Bass may be problematic.

Blair and Dan join forces to track down an MIA Juliet. Chuck begins to suspect Lily isn't telling him the full truth.