"Katherine," Stefan pushes his anger aside in favor of something softer, adopting a pleading, apologetic look. "Don't be like that."

It feels wrong to be doing this in front of Elena, putting on what is and isn't an act with her sitting right beside him. If he could take this conversation somewhere private, he would, but he can't unbind himself from Elena -- in more ways that one. There's guilt sitting on his shoulders like a heavy blanket of snow weighing down the limbs of a tree, and he can't figure out if it's because of what he's doing to Elena or what he's doing to Katherine.

Maybe it's both. When did he become the bad guy in this?