Immediately, Blair gets hurt and quiet, and he apologizes, and goes for the final cut: "I'm not mad at you. It's my own fault. I am everything my father said I was." Which is the final key in the box for a reason, because Blair can't accept the idea that her parents love her, on that yucky level, any more than Chuck can. The one thing she's always tried to do is save him from Bart, because nobody ever saved her. And no matter how much work she and her parents have done to fix it, and they've done admirably, there's still that little voice: Not enough.
Serena's literally flipping weapons around (Eric, recently Stateside, even calls them "nunchaku"!) when Eric comes up to give her support on her failed party, and he's like, "Well, you did steal his phone," and she's like, upset that he ditched her made-up horrible plan, and Eric tells her to put the nunchaku (love him!) away, and then Jenny comes in with bright yellow canary feathers in her mouth, loudly announcing "Sorry we're late, everyone!" but because she is Serena and everybody else is... Everybody else, S doesn't even notice that Jenny is launching a typically Humphrey wuss assault on her life.
It's kind of cool that Lily is out of town for this, but I'm hoping that once the good Doctor vdDubs shows up, Jenny will use her Lily alliance against Serena in a totally brutal way. Aren't you? They kind of went there earlier in the season, but it's never been Jenny v. Serena as equals -- that was a Don't Tell Mom thing -- while Nate and Lily, as people, are both playing fields where that could actually happen. Blair's sort of worn out as Little J's nemesis, just because they're so much alike and have that begrudging respect thing happening, but if Jenny brought the fight to S like I hope she's going to, that's a whole other nasty thing, precisely for this reason: S would never see it coming, no matter how obvious and crazy Jenny was acting.
Serena explains Assassin, snatch the photo, get that person's previous kills, and when you're ghost like Swayze you come back to the Waldorfs' for the actual party. Five minutes to leave the building -- although, sadly, not the block -- and everybody runs off. Jenny twinkles about how she was "in on it," and Serena is not fooled by that shit at all, and when they're alone she asks Nate WTF he was doing running around with Jenny all day when they were supposed to be doing not only a real thing but a fake one. With associated double entendre regarding Jenny's role in all this mystery. It is well done. He runs off, and into Chuck, who is not feeling this stupid game in any way, but explains why in such a dramatic way that Nate doesn't even hear him: "I'm already dead... Although you're welcome to kill me again if you like." Oh, girl.