After a talking to from Rufus, Dan runs off to school give his support to Serena and tell her that he loves her. But she just says that she's not pregnant and is late to meet Blair, so she runs off.
Jenny meets Blair and her posse on the steps, but she has to jump through hoops to make it onto the vaunted upper steps. J decides she doesn't want to put up with Blair's crap and leaves. Serena shows up and we learn that it's Blair whose period is late, and Serena was just buying the test.
The Humphrey kids come home with the good news that Rufus is not going to be a grandfather. Rufus rejoices, but Dan stresses that Serena's reaction to his telling her that he loves her was less than stellar.
Blair brushes off Serena's request to take the test, and it's eating away at S, so she gets it off her chest and tells Dan how Blair may be pregnant with Chuck's love child. Jenny overhears all of this.
At Dan's urging, Serena goes over to Chuck's to tell him about Blair. But she finds out that Blair's been keeping her in the dark, because she had sex with Nate shortly after she got freaky with Chuck.
Next, Serena goes over to Blair's to confront her about Nate. Blair tells her to get lost, ignoring the fact that Serena took a social bullet for her. Eleanor comes by, concerned that Blair is back to bulimic ways.
Finally, Blair takes the test and finds out that she's not pregnant. She calls Serena and the two make up, calling it a clean slate from here.
Meanwhile, Rufus decides to get back on the dating horse. He asks Bex the art dealer out, but Brynn keeps getting in the way. Rufus finally admits to Bex that he's not so good at dating. She gives him a crash course.
Blair tells Chuck that she's not pregnant, and to stay the hell away from her.
Chuck is not to be stopped, however - he texts Gossip Girl with the rumor that B, not S, is the one who may be preggers, and happened to be sleeping with two guys within one week too. Man, he is bitter.
The news hits the website and everyone at school is abuzz. Jenny runs into Nate, who asks her if she knows if the rumors are true or not. Jenny (Taylor Momsen) gives up Chuck, so Nate (Chace Crawford) confronts him and throws him against his limo. Nate tells him to get lost, which seems to seriously upset Chuck.
Blair (Leighton Meester) goes over to Nate's to make amends, but he's not having it. Blair learns Jenny was the tattle and assumes Serena blabbed to Dan, who told his sister. So she's pissed at everyone now.
Blair catches Jenny trying to sit with the posse, and tries to get rid of her. But Jenny and the posse turn their backs on Queen B, who is pretty much dethroned. Even Chuck (Ed Westwick) spurns her in a bar.
Serena asks Dan if he told Jenny the secret. He says he didn't, and she can trust him because ... he loves her! When Serena confides that she didn't know how to respond, Eric tells Serena she must have trust issues with men who say 'I love you' because of their mother's past bad marriages.
Eric also deduces that J likely simply overheard their talking about Chuck and Blair, and that Dan (Penn Badgley) didn't necessarily say anything and betray her trust. Now Serena really loves Dan!
Serena finally asks Dan why he loves her. He lists all the reasons why. And she says it back... but leaves to catch Blair before she flees the country. Serena begs B to be strong and rise above all the gossip, and she promises to stay by her side. B agrees. They hug and we eagerly await a new season.
(Source: TV Fanatic)