basically, kate also had derek at his most vulnerable - emotionally instead of physically, but it’s almost the same. and what did she do? she shat all over it. she exploited him in the worst possible way.

so if i were derek, i would be freaking out internally right about now. what’s this kid gonna do now? what’s he going to say, what’s he going to tell scott, what’s he going to tell allison fucking argent? what’s he going to demand in return for saving my life?

and stiles does nothing.

he doesn’t rub it in derek’s face, he doesn’t say “you owe me.” he’s just like “so you knew [it was a kanima] the whole time?” sounding kind of annoyed, but nothing more. 

the other thing going on with derek’s facial expression (vulnerability, surprise, hauntedness, etc.) is what i talked about in the post i linked to above. i’m not going to go into that, though, just read the post.

#2: the monster

here’s what happens right before derek gives him that oh-so-soulful gaze:

scott: “but [the kanima] is like us?”

derek: “a shapeshifter, yes, but it’s - it’s not right, it’s like a…”

stiles: “an abomination.”

that is so important. stiles, the human, just said “it’s not like you, it’s an abomination.” he said “werewolves are not abominations.” he said “you are not a monster.”

other than the ones in his family, how many humans know werewolves are real? not a lot. and how many of those humans do you think are werewolf hunters? almost all of them.

i’m going into major headcanon territory here, but i’m willing to bet that when derek was growing up, he was told to keep his true self secret at all times. because the humans are dangerous - they’ll hunt you down, lock you up, use you for experiments, call you a terrifying monster just because they don’t understand you. humans tell their children stories about the big bad wolf. derek is the monster under the bed. he’s not human, he’s part animal, and to the humans, he is an abomination.

except.

this is a human kid, looking derek right in the goddamn eye and saying, “you’re not.”

and that is freaking amazing.