Blair and Chuck are the only two people who are allowed to transcend their histories. Every time either of them shows up, he knows, it's only a matter of time until they show their true colors, and now that he and Blair are a team, they have to close ranks on this. So to see Blair going after somebody other than the enemy -- harboring the enemy in fact, which he doesn't know yet -- is not only a betrayal, but a dangerous loss of focus. Especially when Nate's so happy.
"It is of interest to note that the parts of the plant are not only sensitive to the stimulus of their surroundings, but are correlated, or adjusted to each other... If the 'leader,' or main stem, of a tree is destroyed, one or more of the lateral branches will turn upward, in what appears to be an 'endeavor' to perform the functions of a leader. In order words, the destruction of the leader alters the mode of reaction of the lateral branches to the pull of gravity."
Lily stares at a previous wedding photo -- beautiful, black and white; hilariously, Claus/Klaus's face is hidden behind hers as they laugh: she's smiling at the frame, he's looking down, and to your left -- and Serena approaches sadly. "That was by far your best wedding," Serena says, by way of introductory apology. "Who would have guessed nine months later, C/Klaus would have auf'd?" One minute you're in... "Well, the worst thing is I thought he would make me happy." Serena puts her giant, dangerous-looking purse down and sits on the couch's arm. "I thought all of them would. What are you doing here?" Heh, Lily. Serena, on Carter's orders, is there to clear the air. She apologizes once again for deferring Brown, and for going to live at Blair's house. Lily sighs. "I'm not angry at you, Serena. I should have been here this summer to help you with the decision instead of leaving you here with yet another man who doesn't get it." So, I'm off the hook because you've found somebody else to blame? Great parenting. But more importantly, WTF? "You and Rufus are the perfect couple." Lily stands up and runs out the room with a kiss on the cheek, unable to deal with any of that.