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).