"It girl" Serena van der Woodsen has returned to Manhattan after a mysterious and self-imposed exile to boarding school. Serena's best friend, Blair Waldorf, has conflicted feelings about her friend's return since she has enjoyed being the Queen Bee during Serena's absence and might not be ready to relinquish her new position on the social ladder, not to mention the fact that she has always suspected there may be unspoken feelings between Serena and her longtime boyfriend, Nate.

It's the day right after the Kiss on the Lips party and Serena receives a cold reception from her former best friend Blair. Blair reveals that she knows that Serena and Nate slept together, before Serena mysteriously went to boarding school. Then Serena decides to take Dan to Chuck's fundraiser brunch at The Palace. Meanwhile little Jenny asks Blair for advice, and Blair realizes that she maybe gains something by allowing Jenny into her inner circle.

Blair takes matters into her own hands to help Serena with the manipulative and evil Georgina Sparks. Lily, while keeping Rufus in her mind, prepares for her wedding with Bart Bass that is designed to be the Upper East Side's social event of the year. Serena finally tells Dan the whole truth about her past and they try to work things out after Dan has cheated on her, but will it be too late? An unexpected guest shows up at Lily and Bart's wedding. Georgina is sent somewhere where she can do no harm. Blair plans to go somewhere with Chuck.

Blair is over the moon that she is dating royalty and has every intention of becoming a royal herself, but a scheming Chuck has other plans for Blair and her new love, Marcus, when he introduces Blair to Marcus' stepmother who happens to be Catherine. Meanwhile, Nate learns the downside to having an affair with Catherine when he keeps getting caught in his lies and learns his family has gone bankrupt due to his father jumping bail.

The entire Upper East Side of Manhattan is rocked when Bart Bass dies suddenly in a limo accident. Serena and Eric take the news very calmly while Lily has a troubling time despite her mother, Cece's, awkward attempts to comfort her. Chuck begins to blame Lily for his father's death and threatens to reveal a secret that Bart found on her before his accident. Meanwhile, Blair's mother, Eleanor, prepares for her latest marriage to Aaron's father Cyrus.

In a flashback to the 80s, 17-year-old Lily Rhodes gets kicked out of boarding school and runs away to Los Angeles, reconnecting with her parents, Rick and Cece, and sister, Carol. Back in present day, Blair and Nate attend prom together, but the evening doesn't turn out exactly as planned and Chuck and Serena have a little something to do with that. Serena and Lily don't see eye-to-eye over Serena's recent run-in with the law.

On the anniversary of Bart Bass’ death, Chuck wrestles with an issue from the past and a serious car accident rocks the Upper East Side. Dan and Vanessa attempt to navigate their newly complicated friendship. When Jenny is accused of beating up one of her classmates, Eric is faced with a tough dilemma.

Blair must decide whether to meet Chuck at the top of the Empire State Building or risk losing their future together. A Gossip Girl gossip bomb involving Dan explodes Serena and Nate's relationship. Dorota and Vanya welcome their baby. Jenny hits rock bottom. Georgina returns to the Upper East Side...and she has an agenda.

Blair and Serena spent their summer living it up in the belly of the beast: Paris, France. But where there's Paris there's bound to be boutique, Balenciaga, and of course, boy trouble. Unaware of Chuck's shooting in Prague, Blair struggles to forget him; things take a turn, however, when Chuck mysteriously shows up in Paris with a foreign stunning blonde at his arm. Meanwhile Serena contemplates which of her long-time beaus could be the one for her: Dan or Nate? Even on the Upper East Side drama erupts as Dan figures out the baby mama drama with Georgina, and Nate realizes something about himself when he meets fellow Columbia student, the intriguing Juliet.

Blair and Dan join forces to find Juliet. Serena expounds her boarding school experiences to her therapist and discovers the truth behind Juliet's vendetta against her. Meanwhile Chuck suspects Lily has not told him the full truth.

After a brief encounter abroad, Chuck and Blair make a promise to each other about their relationship, which leaves them once again apart. Dan, with some help from an unlikely ally, Georgina, is writing a scathing tell-all book that can only mean trouble. As the sole head of The Spectator, Nate is making his own decisions and is ready to go up against Gossip Girl. As word spreads that Serena is missing, the gang bands together to find her and are shocked by what they find.

In a fashionable farewell to remember, our favorite Upper East Siders join forces for one last soiree, and the shocking identity of Gossip Girl is finally revealed.