The privileged prep school teens learn that Serena van der Woodsen is back in town.

In the wake of the scandalous Kiss on the Lips party, Serena receives an icy cold reception from Blair.

Blair uncovers scandalous information about Serena; Dan sets his sights on impressing the Dartmouth representative.

Dan makes elaborate plans to impress Serena on their first official date; Jenny is invited to the infamous Blair Waldorf sleepover and finds herself in a high-stakes game of truth or dare; Lily discovers Eric missing from his treatment center, and seeks help from her ex-boyfriend, Rufus.

Dan is torn between two girls when his childhood friend Vanessa returns home and declares her feelings for him

Serena and Dan finally acknowledge they are crazy about each other; Jenny discovers a secret about her parents; Blair is once again devastated by Nate's actions.

When Dan finds out that Serena and her family are celebrating Thanksgiving alone, he naively invites them to spend the holiday with his family.

As 'Gossip Girl' posts news of the annual Cotillion Ball to take place on the approaching weekend, Blair decides not to go with Nate, but she finds herself being featured in The New York Times and is enjoying her secret affair with Chuck. Serena decides not to go either, so her grandmother, CeCe, shows up to change her mind. Meanwhile, Jenny volunteers for the ball and Lily takes her under her wing. But the night of The Cotillion is the night of Alison's first art opening, and Rufus and Alison tell Jenny that she cannot attend the ball. Jenny decides to defy them both by secretly attending the dance anyway. Refreshed by Blair's newly buoyant attitude, Nate asks her to the Cotillion and she accepts, which makes Chuck jealous. CeCe tells Lily and Serena that she is sick with lung cancer and her last dying wish is to see Serena go to the ball, and she wants Serena to go with the wealthy Carter Baizen. The snobbish CeCe takes an instant dislike to Dan and she approaches Rufus with an offer pay him to convince Dan not to go with Serena. Dan learns of this and tells Serena that he does not think very highly of CeCe by telling Serena about how CeCe tried to bribe his father to persuade him not to attend. Surprisingly, the skeptic Serena refuses to believe Dan that her compassionate grandmother is a crafty snob, and she ends up going to the ball with Carter... both her and Dan having fallen right into CeCe's ploy. Also, Chuck manipulates Nate into thinking Carter is having an affair with Blair to provoke a fight with him.

Blair's father comes home for the holidays with an unexpected guest; Jenny and Vanessa help Serena plan the best Christmas surprise ever for Dan.

Gossip Girl takes pleasure in reporting that Serena has been spotted buying a pregnancy test, and word spreads like wildfire.

Blair returns to school after losing Queen Bee status; Serena's not fond of living with her future stepbrother, Chuck.

Serena's world is turned upside down when her former partner in crime, Georgina Sparks, returns to Manhattan to stir up trouble.

Georgina reveals the true reason that Serena fled Manhattan for boarding school, and Serena quickly falls back into her old habits.

Blair is thrilled to be dating royalty, but a scheming Chuck has other plans for her; Serena and Dan agree to keep their recent hookups a secret.

Blair sabotages her mother's show at Fashion Week; Dan starts hanging out with Chuck, and learns that a walk on the dark side always has risks.

Serena decides to visit Yale and gets even with Blair. Dan learns that none of his recommendation letters made it to Yale.

Jenny befriends a model, and is encouraged to explore her wild side; Serena is attracted to an artist, Aaron Rose.

Dan tries to get close to Bart Bass to possibly write an exposé, but things get heated when Chuck finds out.

Blair's favorite Thanksgiving traditions are ruined by her mother's new boyfriend; Serena doesn't tell Aaron about her past -- but Dan does.

The teens prepare for the annual Snowflake Ball, a charity event for prep school seniors.

A sudden and tragic event impacts the lives of everyone on the Upper East Side, especially Chuck and the van der Woodsens.

Chuck's uncle, Jack Bass, arrives on the scene; Jenny returns to school and takes on the mean girls.

The seniors try to find out who is worthy of an early admission to Yale; Chuck pairs up with an unlikely ally in his war with Jack over Bass Industries.

Blair comes up with a plan to get revenge on her teacher; Chuck wakes up in a hotel and tries to piece together what happened the night before.

The seniors put on a production of "The Age of Innocence"; 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 existence in favor of a wilder lifestyle.

Serena throws Jenny a party for her 16th birthday, but things get out of control when Poppy Lifton turns the small gathering into a huge social event.

To prove her independence, Serena refuses to leave jail with her mother or her grandmother; Rufus is furious with Lily for having Serena arrested.

Blair begins NYU, determined to keep her Queen Bee status, but Georgina has other ideas; Serena recruits Carter to get even with Chuck.

It's Jenny's first day as Queen Bee; A famous actress, Olivia Burke, is assigned as Vanessa's roommate.

Lily and Rufus move up their wedding, but complications threaten to tear them apart; Chuck discovers a secret Carter has been keeping from Serena; Dan and Vanessa are pulled into one of Georgina's schemes.

Serena helps Chuck open his club, but Blair feels left out; Dan is unnerved watching one of Olivia's sex scenes with a former co-star.

Serena is put in an awkward position when Lily invites Tripp and Maureen to join them for dinner; Blair suspects her mother of keeping a big secret; Jenny gets even with Eric in the most cruel way.

Chuck finds himself once again at odds with his uncle, Jack Bass. Eleanor puts Blair in charge of making sure her latest fashion show is a huge success with an important client. Rufus attempts to get Jenny back on track by volunteering to have her help with Eleanor's fashion show, but the opportunity takes a big turn for the worse when Jenny learns that Agnes will be one of the models.

Chuck and Blair are faced with the most difficult decision they have ever faced as a couple. Serena plans a surprise birthday party for Nate, but Jenny does her best to sabotage Serenas's efforts. Dan and Vanessa's new relationship hits a bump in the road.

Chuck offers to throw a wedding for a very pregnant Dorota who insists that she and Vanya have a traditional wedding before her parents arrive from Poland and find their daughter pregnant and without a husband. Dorota asks Blair and Chuck to be part of the ceremony and walk her down the aisle. Serena tells Nate she is having breakfast with the Humphreys when in reality she's secretly meeting up with Carter Baizen. Rufus discovers that Lily has been lying to him about her whereabouts.

When Lily's ex-husband, Dr. William van der Woodsen, shows up unexpectedly in Manhattan, Serena finally gets the reunion she has so desperately wanted with her father, but the circumstances turn out to be far from ideal. When Serena and Nate continue to have relationship issues, a scheming Jenny is more than happy to be a shoulder for Nate to lean on. Meanwhile, Dan finds out that he didn't get accepted into the Tisch writing program and Vanessa admits she may have been somewhat responsible.

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.

On her first day at Columbia, Blair attempts to gain membership into an ultra-exclusive social club, Hamilton House, but she's in for a few big surprises. Serena begins to suspect that Juliet is intentionally sabotaging Serena's life and that it may have something to do with Nate. Rufus is worried about Dan and decides to take matters into his own hands.

Nate suspects that Juliet is keeping a big secret from him and decides to confront her. Blair schemes to undermine Chuck's newfound happiness. Dan finds himself torn between his feelings for Serena and Vanessa.

An anonymous Gossip Girl blast starts a very damaging rumor about one of Columbia's new students, Serena. On her path to greatness, Blair decides to take a class with a powerful businesswoman, Martha, who is guest-lecturing at Columbia, but a mysterious fellow student thwarts her plans to secure the prized position as Martha's assistant.

Blair is caught off-guard - and not in a good way - by a surprise guest at her birthday party. Having had enough of Chuck and Blair's games, Serena and Nate decide to plan an intervention.

Chuck and Blair decide it's in both their best interests to put the past behind them and end their vindictive games. Nate confronts Juliet after discovering a secret she has been keeping from everyone. Dan and Nate realize they both still have feelings for Serena.

Chuck hosts a "Saints and Sinners" masquerade party at the Empire Hotel. At the party, Dan and Nate don't know what to make of Serena's strange behavior and mixed messages. Blair sets her sights on becoming the new face of Anne Archibald's foundation for girls, but Anne is concerned that Blair's friendship with Chuck Bass may be problematic.

Chuck, Serena, Blair, Dan, Jenny and Eric find themselves faced with a crisis when a member of one of their families is hospitalized. Meanwhile, Nate attempts to help his parents, The Captain and Anne, put their complicated past behind them and reconcile.

A former associate of Chuck's father, Russell Thorpe - along with his daughter Raina - returns to Manhattan with some unfinished business for our Upper East Siders. Serena and Chuck join forces against Lily. Blair realizes that her mother, Eleanor, may be her key to becoming a future CEO. Nate worries that his father, The Captain, is having a little too much fun and not taking his parole seriously.

It wouldn't be a proper Upper East Side party without some major Gossip Girl drama, and for Eric's 18th birthday celebration there is plenty to go around. Blair decides to speed up the time table on her career path to becoming a powerful woman, but ultimately stretches herself too thin. Serena is forced to choose between her family and Ben. Chuck and Lily's relationship remains icy in the aftermath of Lily's betrayal.

Ben's mother comes to town, forcing issues to the surface between Ben and Serena. Russell Thorpe is determined to destroy Chuck's family legacy, but he risks alienating his daughter, Raina, in the process.

As Lily awaits the consequences of her decision, William van der Woodsen, CeCe and Lily's sister, Carol, come into town to support her and be part of a Taschen photo shoot on "modern royalty" in which the Rhodes family is participating. Unbeknownst to Carol, who has always chosen to keep her daughter Charlie far away from the Upper East Side, Charlie has followed her to New York to meet Serena and the rest of the family. Blair has an epiphany about her future, and grapples with the knowledge of whom she's destined to be with.

Serena enlists Charlie to go undercover Gossip Girl-style to determine why Dan and Blair are spending so much time together, and what role an unexpected visitor is playing in their lives. With Nate's help, Raina decides to go on a search for her long-lost mother. Chuck's hopes about his legacy are dashed with the reveal of devastating information from the past.

Blair's dreams appear to be coming true, but Serena threatens to jeopardize it all by dredging up Blair's past. Charlie befriends Vanessa, who may or may not have a hidden agenda. Nate is torn between his relationship with Raina and a truth he must keep hidden out of loyalty to Chuck.

Season four wraps up with an explosive finale, including the return of Georgina Sparks 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.

Serena loves her new job in Hollywood, but makes a costly misstep when she tries to impress her boss. Chuck and Nate arrive in Los Angeles as the last stop of their Lost Summer trip, joining Serena at a glamorous Hollywood Hills party, where Nate meets a sexy older woman. Blair and Louis return from Monaco and begin planning their royal wedding, but when Louis refuses to stand up to his family and support Blair's choices, his weakness threatens their relationship. A magazine is planning to run an excerpt of Dan's book until an unlikely ally steps in to help him kill the story.

Nate reconnects unexpectedly with Diana, who offers him an exciting opportunity. Serena forces Charlie to decide which world she wants to embrace. Dan seeks out Chuck's help to stop the publication of his book, but discovers it is Chuck who needs the help. Blair's future sister-in-law, Beatrice, arrives from Monaco, but her motives with Blair may be more than just to get acquainted.

Nate must decide whether to cross moral lines at Diana's request. Dan has figured out who is publishing his book, and seeks help to stop it, but he ends up in the spotlight anyway. Chuck helps Dan come to terms with his fate, just as Dan continues to try to help Chuck break through his emotional block. Serena and Charlie return to the Upper East Side from California.

After much deliberation, Dan decides to gather Serena, Blair, Nate, Chuck, Rufus and Lily to reveal the truth about his book in the hope that they will support him at his book party. Meanwhile, Blair and Louis hit a crises point after Louis reads Dan's book. Diana learns incriminating information about one of Nate's friends and uses it to her advantage.

Blair makes all of her former minions and Charlie compete to secure the coveted bridesmaid spots in her upcoming royal wedding. Nate is tired of keeping his relationship with Diana secret, so he decides to use Charlie to make Diana jealous. Serena's boss is determined to acquire the film rights to Dan's book, so Serena must put her personal feelings about Dan and the book aside in order to close the deal.

Several of our favorite Upper East Siders attend a performance of Punchdrunk's provocative theater experience, "Sleep No More," which translates to masks, anonymity and some surprising romantic twists by the end of the evening. Meanwhile, Diana sets her sights on Serena in her quest to ruin Gossip Girl. Dan is out on his book tour, but things aren't exactly as they appear to his friends and family.

Lily, Charlie and Serena eagerly anticipate the Studio 54 party being thrown in CeCe's honor. Nate takes on a new role at the Spectator, but his first big story turns out to be about someone he knows all too well.

Lily throws Charlie a party to officially introduce her to New York society. Meanwhile, Charlie's ex-boyfriend, Max, throws a wrench into Charlie's future as an Upper East Side princess. Dan decides it may be time to tell Blair the truth about his feelings for her.

The much-anticipated 100th episode will open with a musical dream sequence featuring Serena, Blair and all the men in their lives. Also, while Chuck wrestles with the reality that Blair is about to walk down the aisle with Prince Louis, the return of Georgina Sparks might make the royal affair a royal disaster.

Blair must make a difficult decision about her future, the consequences of which could hurt those she loves most. Serena takes the blame for an incident with Gossip Girl in order to protect someone she loves. Georgina smells the scent of scandal and decides to follow its trail.

It's Valentine's Day on the Upper East Side and Blair can't resist playing cupid for someone she loves. Georgina is intent on stirring up more drama, so she decides to crash Nate's Valentine's Day party. Meanwhile, Serena is shocked by something she witnesses at the party.

Dan feels honored when he learns that Upright Citizen's Brigade is performing excerpts from his book, Inside. Blair tries to prove Serena's suspicions wrong in order to save their friendship. On her way out of town, Ivy ends up on a collision course with the van der Woodsens.

Blair thinks Cyrus may have found a potential loophole in her prenup. Chuck and Georgina partner up in a scheme, but it has an unpredictable outcome. Meanwhile, a family crisis brings William van der Woodsen back to the Upper East Side.

Chuck invites Jack (DESMOND HARRINGTON) to town, Blair and Dan attempt to consummate their new relationship and Ivy finds an unlikely ally in William (BILLY BALDWIN).

Serena tries to make a reluctant Lola the next It Girl of the Upper East Side, starting with modeling at a Kiki de Montparnasse show.

To celebrate their official coming out as a couple, Blair and Dan host a glamorous British-themed Salon, including guests Julian Tepper and Jenna Gribbon (founders of The Oracle Club). Lola lands the audition of a lifetime, but Gossip Girl may have other plans for the Upper East Side's latest It Girl. Meanwhile, Lily and Rufus disagree over the best way to handle the Ivy situation, and Serena and Diana face-off over secrets they both would prefer remain secrets.

Blair feels like her Upper East Side status might be slipping away and devises a plan to assure that doesn't happen. Meanwhile, Lily throws a family gathering - including William, Carol and Lola - in an attempt to prove the van der Woodsen family is as united as ever. Finally, Nate digs into Diana's past and is surprised by what he discovers.

Chuck, Nate, Blair, Serena and Lola team up to uncover what they think is an explosive secret between Diana and Jack. Meanwhile, Dan is offered a prestigious fellowship in Rome for the summer.

Serena poses as Blair at an important meeting. Ivy and Lola (ELLA RAE PECK) team up to help Chuck. Nate makes a decision about the future and Diana (ELIZABETH HURLEY).

When Gossip Girl goes after Blair as she's never done before, Serena admits she may have unintentionally played an important role in Blair's latest nightmare. Meanwhile, Nate invites Lola to move in with him, and Lily must make a big decision about the future of her marriage. Finally, by episode's end, Blair will make a choice between the two men in her life... will it be Chuck or will it be Dan?

Serena hosts a big gala, Blair prepares to debut her new fashion line and Dan must decide if he is willing to sacrifice hisintegrity in order to get his work published.

Feeling the pressure to make her first Waldorf Designs fashion show a success, Blair must rely on help from an unlikely source, but some unexpected scheming causes a scandal on the runway. Serena discovers that befriending Steven's daughter Sage is trickier than she thought, especially when she is forced to put her issues with Blair aside to make Sage happy. Nate publishes Dan's first serialized article causing a stir and producing a serious threat. Meanwhile, Chuck begins to look into the clue that Amira left behind, which may help uncover what Bart is hiding.

Eleanor gives Blair an ultimatum; Serena worries about Steven's attitude toward her; Dan publishes another article.

With Ivy's help, Chuck discovers there is evidence incriminating his father and enlists Nate to help retrieve it. Serena volunteersto help Dan, but unexpected emotions arise.

Serena and Dan decide to make amends with those they have wronged. Chuck is close to getting the evidence he needs against his father, but a close ally reveals his plan.

What's Thanksgiving without a side of drama? Serena and Dan throw their first Thanksgiving together, but everyone seems to havetheir own agenda.

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

Chuck offers to throw a wedding for a very pregnant Dorota who insists that she and Vanya have a traditional wedding before her parents arrive from Poland and find their daughter pregnant and without a husband. Dorota asks Blair and Chuck to be part of the ceremony and walk her down the aisle. Serena tells Nate she is having breakfast with the Humphreys when in reality she's secretly meeting up with Carter Baizen. Rufus discovers that Lily has been lying to him about her whereabouts.

Blair comes up with a plan to get revenge on her teacher; Chuck wakes up in a hotel and tries to piece together what happened the night before.

Serena is put in an awkward position when Lily invites Tripp and Maureen to join them for dinner; Blair suspects her mother of keeping a big secret; Jenny gets even with Eric in the most cruel way.

Chuck, Nate, Blair, Serena and Lola team up to uncover what they think is an explosive secret between Diana and Jack. Meanwhile, Dan is offered a prestigious fellowship in Rome for the summer.

Chuck and Blair are faced with the most difficult decision they have ever faced as a couple. Serena plans a surprise birthday party for Nate, but Jenny does her best to sabotage Serenas's efforts. Dan and Vanessa's new relationship hits a bump in the road.

Several of our favorite Upper East Siders attend a performance of Punchdrunk's provocative theater experience, "Sleep No More," which translates to masks, anonymity and some surprising romantic twists by the end of the evening. Meanwhile, Diana sets her sights on Serena in her quest to ruin Gossip Girl. Dan is out on his book tour, but things aren't exactly as they appear to his friends and family.

Devastated by the recent plot twist in her life, Blair turns her back on her predictable existence in favor of a wilder lifestyle.

Serena throws Jenny a party for her 16th birthday, but things get out of control when Poppy Lifton turns the small gathering into a huge social event.

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.

An anonymous Gossip Girl blast starts a very damaging rumor about one of Columbia's new students, Serena. On her path to greatness, Blair decides to take a class with a powerful businesswoman, Martha, who is guest-lecturing at Columbia, but a mysterious fellow student thwarts her plans to secure the prized position as Martha's assistant.