S4, E9: 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 (recurring guest star FRANCIE SWIFT – The Good Wife) foundation for girls, but Anne is concerned that Blair's friendship with Chuck Bass may be problematic. Recurring guest star KATIE CASSIDY appears as Juliet.