Lily and Rufus decide to move up their wedding to the next day, but will someone or something come between them before they become man and wife? Chuck discovers a secret that Carter has been keeping from Serena. Dan and Vanessa are pulled into one of Georgina’s schemes. Blair is suspect of Bree and shares her concerns with Nate.

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.