Season four’s main mystery revolves around Juliet Sharp (Katie Cassidy), a secretive girl with an agenda against Serena involving her past. The second half of the season builds on the complications of Serena’s new found relationship with her former teacher Ben, Chuck trying to regain control of Bass Industries from Russell Thorpe (Michael Boatman), and Dan and Blair’s growing friendship. The season also focuses on Lily’s past betrayals coming back to haunt her; Chuck and Blair’s tumultuous relationship after their break up; Dan and Vanessa’s deteriorating friendship; and the arrival of Serena’s cousin Charlie Rhodes (Kaylee DeFer) to the Upper East Side.
The first two episodes of the season took place with Serena, Blair, and Chuck in Paris. While in Paris, Blair meets Prince Louis Grimaldi, to whom she later becomes engaged at the end of the season.
Episode 1 : Belles de Jour