Gossip Girl (season 4) (2010)

Season four begins with Serena and Blair enjoying their summer in Paris...until the unexpected appearance of Chuck Bass, who is using a false name and cozying up to a new girl. Blair has to decide if she wants to fight for Chuck or spend her energy trying to rule Columbia University. Serena needs to choose between Nate and Dan, but Dan is a bit busy coping with his new role as "dad" to Georgina's baby. Georgina later reveals the baby is not his. Stephanie Savage has revealed in an interview that the Dan and Serena story is "reactivated" and sorting through it will become a bigger story. She also revealed that the third season finale "Last Tango, Then Paris" had a big impact on Jenny and she'll be a changed person when she returns. Her return later this season will be "full of drama."

The Gossip Girl website was under construction when Serena and Blair returned from Paris and debuted “never before seen technology" when it returned. It is revealed that Juliet is working with her brother to take down Serena, for unknown reasons. Vanessa gets caught in the middle when Juliet sets her up for stealing Serena's phone and sending an incriminating email. Vanessa later leaves town when only Dan believes her, but tells Juliet to watch her back. After Blair ran Chuck's new girlfriend out of town, he pledges war against her. They later decide that it's best for both of them if they end their fighting after Jenny posts on Gossip Girl the reason why she left town. In the next episode, at Blair's 20th birthday party they kiss and have sex. Both Nate and Dan still have feelings for Serena, but don't know what to make of her mixed signals.

Most of Juliet's plan will be revealed by the end of the first half of the season, with some elements set to carry over. Juliet will also recruit two main characters to help take Serena down. Blair and Dan will team up to help Serena. The two characters who joined Juliet were Vanessa and Jenny. The three manage to turn everyone against Serena when Juliet and Jenny dress up as her at a masquerade party. Juliet takes photos of herself with cocaine and drugs Serena, causing Lily to believe Serena had gone off the rails again and has her committed to the Ostroff center. Jenny, feeling guilty about what they've done reveals everything to Blair. Vanessa leaves town to avoid Blair, while Blair and Dan form an alliance to seek revenge on Juliet. After they track her down, Juliet goes to Serena and explains everything to her. It is revealed in a confrontation with Lily that Juliet's brother Ben was Serena's former teacher at her boarding school in Connecticut, who was accused of having an affair with Serena. Lily forged Serena's signature on the police affidavit, which in Lily's plan, would allow Serena to return home and, inadvertently, sent Ben to prison. Serena then hatches a plan to help free Ben from prison. This involves proving that her mother forged the affidavit against Ben. Chuck also learns that Lily was planning to sell Bass Industries behind his back.