MONDAY, JULY 27

"GOSSIP GIRL" � (9:00-10:00 p.m. ET)

"The Age of Dissonance" (TV-14, DL) (HDTV)

THE SENIORS PUT ON A PRODUCTION OF "THE AGE OF INNOCENCE"/SEBASTIAN STAN ("KINGS") RETURNS AS CARTER BAIZEN � The Constance Billard and St. Jude seniors put on a production of "The Age of Innocence" and find their personal lives mirroring conflicts in the play. Serena (Blake Lively) develops a crush on the play's director, Julian (guest star Harmon Walsh), and enlists Vanessa's (Jessica Szohr) knowledge of theater to help her get the otherwise uninterested guy's attention. Blair (Leighton Meester) receives devastating news about her future that leads her on a witch-hunt for the person responsible. Dan (Penn Badgley) and Rachel (guest star Laura Breckenridge) agree to stay away from each other in the aftermath of being discovered as more than teacher and student, but find it impossible to keep that promise. Chuck (Ed Westwick) enlists help from an unlikely source, his nemesis Carter Baizen (guest star Sebastian Stan). Chace Crawford, Taylor Momsen and Matthew Settle also star. Norman Buckley directed the episode written by Jessica Queller (#218).