Serena begs him to man up for like the eighth time this week, and he desperately moans through the tears and violent shaking that his future rides on not getting expelled, blah blah, we get it, you're the only person who ever appreciated anything ever and that's just so ironic because you also are the only person who was never given anything at all that you didn't wrench from the soil with your rough hands, whatever. Finally Serena's like, and I'm paraphrasing here, "It was me, you idiot. And the only reason I didn't tell you is that you are a douchebag of truly staggering proportion." He's like, "What? Me judgy?" Um, every moment. He fully goes, "Aren't we past that?" Um, past the part where you totally keep tabs on everything your girlfriend does and inform her at ten-minute intervals, chest puffed out, where she's scoring on your big fat stupid legal pad of ethical behavior? Wouldn't that be a scream. And again: don't get mad at me, I don't hate Dan. She's in it for the exact same reason, and it's even grosser: what she wants most is a big fat legal pad of ethical behavior, because they didn't give her one when she was a kid, because she was raised by wolves, and if she's ever going to stop hating herself, she needs to know she's measuring up.
Serena puts a really gentle, loving spin on this, about how she didn't tell Dan because she didn't want to put him in the position of choosing himself or her. He's been acting like a wolverine and begging for a reason to snitch the whole time, because those UES kids will fuck you over if you don't watch yourself, but now he's in an eff-or-get-effed position, because he does love Serena. And that is...pretty good story, actually. They talk about how she got them into the pool, and of course he's totally accusatory but at least she calls him on it this time, and she explains how freshman year she dated the swim team captain, and he gave her a key so they could fuck in private. Dan, of course, nearly runs shrieking from the entire concept that Serena dated before they met, but manages to keep his seat. So Saturday night, Blair and Serena "ran out of places to go," which is an awesome and useful turn of phrase for this situation, and Blair remembered Serena's key. And the rest you already know: like every party that ever happened to teenagers since the invention of television, two became four became a billion, and somehow this means that Serena attempted to murder a boy in cold blood. Which again, that's so totally Serena; all she wanted in the entire universe was to wear a cute swimsuit, flirt with her boyfriend, and not get raped by her stepbrother, and now she's killing sophomores without even trying. Every week this happens, and every week she's like: "Isn't that so crazy?"