Blair has been mysteriously absent after she lost the baby, which lead Louis and Chuck to suspect her of having an affair. Eventually they find out that she spends a lot of time with Dan - but is it for the reasons they think? Nonetheless, Blair asks Dan to keep it a secret, which leaves him in an awkward position, especially since all of their friends demand to know why Blair acts as she does.
Blair prepares to celebrate her upcoming royal wedding with a bachelorette party, but others scheme behind her back to make this a night to remember. After discovering the truth behind Chuck and Blair's car accident, Nate joins forces with a surprising ally to gather the evidence. Serena and Dan pretend to be dating again to protect someone close to them.
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.
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.
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?
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.