SPOILERS SPOILERS

http://www.youtube.com/watch?v=7jkZUZ00Alk
Summary:
When Serena (Blake Lively) notices that Dan (Penn Badgley) has been cozying up to the new girl in school, Amanda (guest star Laura-Leigh), the ever-loyal Blair (Leighton Meester) and her minions decide to befriend Amanda and sabotage her budding new romance with "lonely boy." Vanessa (Jessica Szohr) discovers a scandalous secret about Catherine (guest star Madchen Amick) and enlists Blair’s scheming expertise to use the information to help Nate (Chace Crawford). Meanwhile, Lily (Kelly Rutherford) finds herself drawn back to her ex, Rufus (Matthew Settle), once again. Taylor Momsen and Ed Westwick also star. Jim McKay directed the episode written by Robby Hull.

Spoilers:
[Catherine] disappears at the end of episode 4, although Josh Schwartz says the "door is open" for her to return.
When Serena notices that Dan has been cozying up to the new girl in school, Amanda (guest star Laura-Leigh), the ever-loyal Blair and her minions decide to befriend Amanda and sabotage her budding new romance with "lonely boy." Vanessa discovers a scandalous secret about Catherine (guest star Madchen Amick) and enlists Blair's scheming expertise to use the information to help Nate. Meanwhile, Lily finds herself drawn back to her ex, Rufus, once again. Taylor Momsen and Ed Westwick also star.
Blair and her "court" interview different girls in order to decide if they'll be included in their little private group. At school, Dan runs into new student Amanda. They bond over their passion for books. Blair and her friends warn Amanda that hooking up with Dan could be dangerous for her health, socially, emotionally and physically.
Blair then tells Amanda that she should join her group. Dan, Amanda and Serena meet up later that night. Dan and Amanda continue to bond. Serena won't be alone for long since Penelope will introduce Serena to Jenns, the Abercrombie-Fitch-type captain of the Dalton Lacrosse team. Vanessa wants to have a chat with The Duchess.

xoxo RayRay