Imo

I think the boss asked emma to stay behind and be the next one to watch over the "borders" to make sure no one crosses. If that's so we'll probably se a Rambo/Lara Croft emma having to face demons degenerated to animal-kind all by herself for the rest of her life. Just a guess but she really thought it through so the shocked face has to be for something really upsetting and unpredictable