Blair Waldorf (Leighton Meester) has spent a fabulous summer with her fiancé, Prince Louis (guest star Hugo Becker), in her future kingdom of Monaco. But when Blair returns home from the holiday, this Princess-to-be will quickly learn that planning a royal wedding can be a royal pain. And the fallout from Blair and Chuck's (Ed Westwick) heartbreaking decision to let each other go isn't making life easier.

Meanwhile, Serena van der Woodsen (Blake Lively) scored the perfect summer job in sunny Los Angeles, working for an A-list director. Being in California has clearly allowed Serena to discover a new sense of purpose, but will the return of her cousin Charlie (Kaylee DeFer), in actuality a struggling actress Aunt Carol paid to impersonate her daughter, threaten to ruin everything? Only time will tell.

Chuck Bass and Nate Archibald (Chace Crawford) enjoyed a hedonistic summer trip around the globe but, when they stop in Los Angeles to visit Serena, things quickly spin out of control. Nate falls into bed with a sexy and mysterious older woman, Diana Payne (guest star Elizabeth Hurley), who has more in store for him than he knows. And a seemingly carefree Chuck is chasing down exotic adrenaline rushes that might put his life in real danger.

After a relaxing summer in the Hamptons, Dan Humphrey (Penn Badgley), has his whole world shattered when he discovers that Vanessa has gone behind his back and found an editor to anonymously publish his autobiographical novel, INSIDE. Dan's terrified of all his friends and family reading his critique of New York high society, but will he say no to the fame and fortune that comes with being a published author? It's anybody's guess.

So watch out Upper East Siders, this season nobody's safe, and everybody's going to be sorry�.XOXO Gossip Girl.

Filmed in New York and based on the popular series of young-adult novels by Cecily von Ziegesar, "Gossip Girl" is from Fake Empire and Alloy Entertainment in association with Warner Bros. Television and CBS Television Studios with executive producers Josh Schwartz ("Chuck," "The O.C."), Stephanie Savage ("The O.C."), Leslie Morgenstein ("The Vampire Diaries"), Bob Levy ("The Vampire Diaries") and Joshua Safran.