B swears she didn't do it, and Serena's like, "At least have the dignity not to lie to my face," and B swears again. S points out that of all his faults, Dan wouldn't do that shit, and Blair totally would, and they're the only ones that knew it, so it's Blair. She full-on goes, "I always want to believe the best in you, Blair. The bottom line is, betrayal's in your nature," and stomps away again. Which is fucked, because the only thing that technically keeps Blair alive is Serena's love and that's always been true. So you've got Yale, and you've got Serena, and you've got vengeance, and that's all Blair's ever had, because the world is a dry and empty, scary place for her and she scrabbles on the rocks for every grip she's got, literally. It's soapy drama unless you really think about this part, because: Yale's down, and Serena is saying that every time she told Blair she was good ("Oh, it looks so good! You're doing so good! You got it! Look how good you are!") was a lie the whole time, they were just fooling themselves.
I didn't know what to do with my hands, I didn't know how to hold myself onstage, I couldn't control my voice.
The music gets schemey and Blair pulls her version of it together, realizing that in fact her enemy is Dan, who would have heard about Lord Marcus from Vanessa, and is now getting her back for Teachergate. She grabs Dorota by the dress and screams, "Do you know how hard it is to get revenge when your enemy is changing every five minutes?" Dorota tells her to chill and drink some tea for her vocal chords, and Blair hisses and goes after Dan this time.
Dan surprises Rachel in the hallway because now Rufus actually parenting is some kind of Romeo + Juliet thing in his head, and he drags her into the costume closet so they can "talk," which means fuck, but instead of just getting down to it they play out the exact same carriage scene as Dan's about to play onstage with Blair, up to and including kissing Rachel's wrist and saying, "You know this can't last, our staying away from each other." And it's hot and whatever, her stupid charm bracelet weighs more than she does and she's probably got a tattoo of a Japanese character somewhere on her skinny ass, but whatever. Dan Humphrey macking down in an old-timey tuxedo is the third-hottest thing in this episode after Julian and Nate's upcoming hissyfit.