Joanne Whalley

"The Backup Dan" begins with Blair and Dan successfully fleeing all the way to the airport to make their escape from New York. Elsewhere on the Upper East Side, Georgia has discovered some scandalous gossip and her newly revealed nature means she will not be letting it get away from her.

As Blair prepares to walk down the aisle, Chuck tries to come to grips with losing the love of his life. Michelle Trachtenberg returns as Georgina to cause trouble, plus other surprises in the 100th episode.

Serena loves her new job in Hollywood, but makes a mistake trying to impress her boss. Chuck and Nate arrive in LA as their last stop of their Lost Summer trip, joining Serena at a glamorous party, where Nate meets a sexy older woman. Blair and Louis return from Monaco and begin planning their royal wedding, but when Louis refuse to support Blair's decisions against his family, their relation is at risk. A magazine is planning to run an excerpt of Dan's book until an unlikely ally helps him.

In the season four finale, will Blair choose her prince or her dark night?
The finale includes the return of Georgina and Constance Billard mean girls Kati and Is, a cameo by "Gossip Girl" author Cecily von Ziegesar, a performance by Airborne Toxic Event and, oh yeah, a few very juicy cliffhangers.