WILL LILY & RUFUS GO THROUGH WITH THEIR PLANNED NUPTIALS? / SONIC YOUTH PERFORMS IN THE EPISODE / HILARY DUFF AND MICHELLE TRACHTENBERG GUEST STAR — Lily (Kelly Rutherford) and Rufus (Matthew Settle) 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 (Ed Westwick) discovers a secret that Carter (guest star Sebastian Stan) has been keeping from Serena (Blake Lively). Dan (Penn Badgley) and Vanessa (Jessica Szohr) are pulled into one of Georgina's (Michelle Trachtenberg) schemes. Blair (Leighton Meester) is suspect of Bree (guest star JoAnna Garcia) and shares her concerns with Nate (Chace Crawford). Taylor Momsen also stars.