As the summer draws to a close in the Hamptons, Serena and Nate have everyone fooled into thinking they are a couple to cover up the fact that Nate has been hooking up with an older woman. Blair returns from abroad with an attractive man on her arm, Marcus, making a very jealous Chuck question his decision to leave Blair stranded at the heliport. Dan has spent the summer assisting a famous author, and clearly still has a certain girl on his mind, which results in him going after her. While interning for Eleanor Waldorf's company, Jenny sneaks a coveted invite to the Hamptons' White Party and meets socialite Tinsley Mortimer.

Blair is delighted that she is dating royalty and falls in love with idea of being a royal, while scheming against both Chuck and Marcus. Serena and Dan agree to keep their recent hook-ups a secret from their friends and family until they figure out what all this means for their relationship. Meanwhile, Nate learns the downside to having an affair with a hot older woman, Catherine, who also happens to be married.

Stuck in a citywide blackout, the teens are forced to confront their problems in time for the start of the new school year. Blair and Chuck are concerned about the lack of passion in their new relationships. Being trapped in an elevator forces Serena and Dan to bring up the issues they faced in junior year. Nate is torn between his affections for Vanessa and his increasingly complicated relationship with Catherine. Meanwhile, Jenny faces losing her internship when Eleanor catches Jenny criticizing one of her designs.

The school year has started for the students of Constance Billard and St. Jude. Blair and her minions decide to befriend the new girl Amanda in order to sabotage her for coming in between Serena and Dan. Vanessa discovers a scandalous secret about Catherine and enlists Blair's scheming expertise to use the information to help Nate. Meanwhile, Lily finds herself drawn back to her ex, Rufus, once again.

In the midst of Fashion Week, Blair is outraged when she discovers that Eleanor has given Serena and her new socialite friend, Poppy Lifton, front-row seats to the Eleanor Waldorf show at the advice of her protégée Jenny. Blair decides to ruin the event after being hurt by Serena's popularity and her mother's betrayal. Meanwhile, Dan begins hanging out with Chuck, but a walk down the dark side always comes with costs, as Dan discovers the hard way. Lily discovers a secret her new husband, Bart, has been hidden from her.

Following the fight after the fashion show with Blair, Serena decides to get revenge by canceling her intentions to visit Brown and accepting a personal invitation to visit Yale from the Dean. Dan resorts to desperate ways to get into Yale after realizing that his reference letters were never sent. Chuck is kidnapped by Skull and Bones members while visiting Yale, and Nate meets a student who may hold the key to Dan's acceptance.

Vanessa continues to use the photograph of Catherine and Marcus to blackmail Blair, which prompts Blair to retaliate. Lily and Bart organize a lavish housewarming celebration and expect their children to make them proud in front of the assembled press, but a rebellious Serena refuses to play by their rules. Meanwhile, Dan and Jenny uncover a major truth that Nate has been keeping hidden from his friends.

Jenny befriends a young model, Agnes, who encourages Jenny to not only explore her wild side, but also to confront her fears no matter who gets hurt. Serena meets an artist, Aaron Rose, and realizes they have instant chemistry. Blair enlists the avice of Dan to help her seduce Chuck, but it proves tougher than she ever imagined.

Serena realizes Aaron has been keeping a secret from her. Blair babysits the 15-year-old daughter of a Yale donor who has bit of a wild side. Meanwhile, Jenny and Agnes plan a guerrilla fashion show that will either launch Jenny's fame or ruin her chances of ever being accepted by the industry. Dan and Vanessa learn the secret between Jenny and Nate.

Not approving of the new man in her mother's life, Cyrus Rose, Blair makes it her mission to split up the two lovebirds. After running away from home, Jenny moves in with Agnes as the friends move forward with their plans for a fashion line. Serena continues to fall for the new guy in her life, Aaron, but she learns something about him that threatens to end things just as they are getting good. Dan decides to win the trust of Bart Bass in order to learn more about the man and possibly write an exposé on him for Vanity Fair, but things get heated after Chuck finds out the real reason Dan is spending so much time around his family. Singer Cyndi Lauper makes a cameo at Blair's 18th birthday party celebration.

Thanksgiving in the Waldorf household finds Blair upset that her mom's new boyfriend, Cyrus, has decided to ruin all her favorite traditions, but that is nothing compared to what is coming next. Lily finds herself trying to broker a peace between Rufus and Jenny as their relationship is given an ultimatum. As Serena tries to keep her past a secret from her new man, Aaron becomes curious and seeks help from Dan. Vanessa and Chuck come to their friend's aid when Nate is once again forced to confront his father's abandonment. Finally, Eric discovers a secret that Bart has been keeping from Lily.

The annual Snowflake Ball has arrived for the students of St. Jude and Constance Billard. Blair and Chuck decide to test how well they know each other, which ends with them finding doppelgängers of themselves. Aaron's ex-girlfriend, Lexi, expresses an interest in Dan. There is drama between Serena and Dan about their sex lives. Nate, Jenny and Vanessa get into a tangled situation that puts their friendships and hearts on the line, as Vanessa steals a love letter Nate had written to Jenny and continues her relationship with Nate. Jenny retaliates by sending an unsuspecting Vanessa to the ball in a see-through dress. After the ball, Nate ends things with Jenny and goes after Vanessa. As Bart Bass is trying to return to the Snowflake Ball, he suffers a car accident.

A sudden and tragic event hits the Bass family with the passing of Bart Bass. The whole city is shocked, including Lily. Chuck does not react very well to the passing of his father. Blair has something important to say to Chuck, but it is said at a bad time. Right before Serena travels to Argentina with Aaron, Dan decides to express his feelings for her. Meanwhile, Cyrus and Eleanor get married, and Rufus discovers something that Lily has been keeping from everybody for a long time.

With Chuck missing since after his father's funeral, Jack arrives on the Upper East Side to help Chuck pick up the messy pieces, but first he has to find him. Trying her best to forget her last painful exchange with Chuck, Blair focuses her attention on being accepted into the most prestigious ladies' club in the city, the Colony Club. Jenny returns to Constance Billard and immediately takes on Penelope and her posse of mean girls, but no one is going down without a valiant Gossip Girl-worthy fight. Meanwhile, after Serena tells Dan about her recent break-up, they decide to get back together.

With the reading of Bart Bass' will, Chuck, Bart's brother Jack, and Blair learn the fate of the Bass empire. Rufus and Lily's relationship is strained as Rufus seeks details about the child he never knew he had. Noticing that his father has been acting strangely as of late, Dan does some investigating and uncovers Rufus and Lily's secret, putting him in the awkward situation of deciding what to do with this shocking revelation and whom to share it with.

It is that stressful time of year when Constance Billard and St. Jude's students find out who is and is not worthy of early admission to Yale University. Serena bonds with her new Shakespeare teacher, Rachel, who has no clue the wrath she is about to suffer after giving Blair the first B of her prep school career. Chuck pairs up with an unlikely ally in his war against Jack over Bass Industries. Meanwhile, Nate and Vanessa have a romantic night at the opera.

In retaliation for not playing by the unspoken rules of Constance Billard, Blair hatches a plan to bring down her teacher, Rachel. After Chuck wakes up in a hotel and only has a minor recollection of what happened the previous evening, Nate and Vanessa try to help him fill in the missing pieces. Blair starts a rumor about Dan and Rachel, which gets Rachel fired. Dan and Serena decide to break up and Dan has sex with Rachel, as she is no longer a teacher. Unaware of this, the school reinstates Rachel.

The seniors put on a production of The Age of Innocence and find their personal lives mirroring the play. Serena develops a crush on the play's director, Julian, and enlists Vanessa's knowledge of theater to help her get his attention. Nate has difficulties with the play and his relationship with Vanessa. Blair receives devastating news about her future that leads her on a witch-hunt for the person responsible. Blair thinks it is Dan, but it turns out to be Rachel. Dan and Rachel agree to stay away from each other in the aftermath of being discovered as more than teacher and student, but find it impossible to keep that promise, and end up having sex before the show. Chuck stumbles upon a secret society and is put into a dangerous situation to try and protect his new love interest. Chuck enlists help from an unlikely source, his nemesis Carter Baizen.

Devastated by the recent plot twist in her life, Blair turns her back on her predictable Waldorf existence in favor of a more wild lifestyle, causing Serena and Chuck to have serious concerns about her new lover, Carter Baizen. Vanessa convinces Nate that it may be time to forgive and forget when it comes to his mother's Kennedy-esque family, the Van der Bilts, who abandoned Nate and his mother when they needed them the most. In a misguided effort to be completely honest with each other, Lily and Rufus agree to share lists of their past lovers.

Serena decides to throw Jenny an intimate party for her 16th birthday, but things get out of control when Serena turns the small gathering into a party. An angry Jenny writes a post to Gossip Girl, turning the party into a huge social event. In a moment of weakness, Vanessa agrees to help Chuck with a scheme having to do with Blair and Nate. Rufus learns that Dan will not receive financial aid at Yale and tries to figure out another way to cover the cost of his education. The episode ends with Chuck and Vanessa starting a friends with benefits, and Nate and Blair starting a relationship.

Serena returns from her trip to Spain with Poppy and Gabriel. Blair makes a secret deal with Nate's grandfather, William van der Bilt, and Nate learns some disturbing information about his father's arrest. Dan takes a job as a cater-waiter to earn money for college, but is distressed when he discovers the gig is a Passover Seder at the Waldorf penthouse and several of his friends and family are guests.

Georgina Sparks returns to the Upper East Side after undergoing a major transformation. Chuck and Nate find themselves at a major crossroads in their relationship as it pertains to their mutual interest in Blair. Serena finds her relationship with Gabriel growing more and more complicated.

Blair pressures Georgina into making amends for her past bad behavior by helping her with a scheme. The rivalry between Nate and Chuck over Blair comes to a head. Lily hatches a secret plan to help Rufus with Dan's college tuition.

In a flashback to the 1980s, 17-year-old Lily Rhodes gets kicked out of boarding school and runs away to Los Angeles, reconnecting with her estranged older sister, Carol. Back in the present day, Blair and Nate attend their senior prom together, but the evening does not turn out exactly as planned due to Chuck's tricks. Serena and Lily do not see eye-to-eye over Serena's recent run-in with the law.

Title reference: The 1983 film Valley Girl.

Gossip Girl plans to spice things up during the graduating class' final days of high school by spreading a tidal wave of juicy secrets. Meanwhile, Lily and Rufus decide to take a significant step. With the seniors leaving, Jenny's reputation is up in the air as Blair and her minions decide to choose one incoming Juniors to fill the Queen Bee position. Chuck makes a shocking revelation to Blair, and Nate wants to spend the summer rebelling against his family.