Great minds! I already found it on Netflix. I think there's a portion of it where Mr. Argent talks about how unusual it is for there to be fireflies. In hindsight, maybe he knew it was a sign even then.
Well, Scott, Allison, Stiles, and I are left. The three of them sacrificed themselves, which might be the common reason why they haven't been touched. And show-me has the fox-shape as protection, according to what little we know so far. Death connects you all, too. Derek lost his family and killed Paige, Ethan and Aiden killed their packs and Boyd, Isaac lost his family, and you are drawn to death. Of course, that's assuming that the three of them are being left out for some reason and I'm being protected.