It’s an Upper East Side face-off when Blair (Leighton Meester) and Chuck (Ed Westwick) both set their sights on a particular item up for bid at Sotheby’s and the personal stakes are high. Serena (Blake Lively) suspects that Carter (guest star Sebastian Stan) may be up to his old habits, Georgina (Michelle Trachtenberg) takes an interest in Dan (Penn Badgley), and Vanessa (Jessica Szohr) begins to suspect that something isn’t quite right with Scott (guest star Chris Riggi). Chace Crawford, Taylor Momsen and Matthew Settle also star. Jean DeSegonzac directed the episode written by Robert Hull.

As the summer is drawing to a close, Blair (Leighton Meester) and Chuck (Ed Westwick) are madly in love and adjusting to their new “in a relationship” status, breaking all traditional rules of dating as would be expected. Serena (Blake Lively) returns from her European adventure with many secrets to hide and a complicated relationship with Carter Baizen (guest star Sebastian Stan). Nate (Chace Crawford) returns from his travels with a mysterious brunette, Bree Buckley (guest star JoAnna Garcia) in tow. Rufus (Matthew Settle), Dan (Penn Badgley) and Jenny (Taylor Momsen) spent the summer in the Hamptons, adjusting to the van der Woodsen’s glamorous lifestyle surprisingly faster than any of them expected. Jessica Szohr also stars. J. Miller Tobin directed the episode written by Joshua Safran.

In a flashback to the 80s, 17-year-old Lily Rhodes (Snow) gets kicked out of boarding school and runs away to Los Angeles, reconnecting with her parents, Rick (McCarthy) and Cece (guest star Cynthia Watros, “Lost”), and sister, Carol (Ritter). Back in present day, Blair (Leighton Meester) and Nate (Chace Crawford) attend prom together, but the evening doesn’t turn out exactly as planned and Chuck (Ed Westwick) has a little something to do with that. Serena (Blake Lively) and Lily (Kelly Rutherford) don’t see eye-to-eye over Serena’s recent run-in with the law. No Doubt performs in the episode as an 80s band called “Snowed Out.” Penn Badgley, Taylor Momsen, Jessica Szohr and Matthew Settle also star. Marc Piznarski directed the episode written by Josh Schwartz & Stephanie Savage

Georgina (guest star Michelle Trachtenberg, “17 Again”) returns to the Upper East Side after undergoing a major transformation. Chuck (Ed Westwick) and Nate (Chace Crawford) find themselves at a major crossroads in their relationship as it pertains to their mutual interest in Blair (Leighton Meester). Serena (Blake Lively) finds her relationship with Gabriel (guest star Armie Hammer) growing more complicated. Penn Badgley, Taylor Momsen, Jessica Szohr, Kelly Rutherford and Matthew Settle also star. Patrick Norris directed the episode written by Leila Gerstein

Serena (Blake Lively) decides to throw Jenny (Taylor Momsen) an intimate party for her sixteenth birthday, but things get way out of control when Poppy Lifton (guest star Tamara Feldman) turns the small gathering into a huge social event. In a moment of weakness, Vanessa (Jessica Szohr) agrees to help Chuck (Ed Westwick) with a scheme having to do with Blair (Leighton Meester) and Nate (Chace Crawford). Rufus (Matthew Settle) learns that Dan (Penn Badgley) will not receive financial aid at Yale and tries to figure out another way to cover the cost of his education. Kelly Rutherford also stars. Armie Hammer guest stars as Poppy’s boyfriend, Gabriel. Allison Liddi-Brown directed the episode written by Sarah Frank-Meltzer.