We can't get through. When I found Deaton, when you went to Derek's with everyone, he was surrounded by a ring of mountain ash. Stiles' dad saved him by shooting him down. Humans can get through but werewolves can't. [ Which is why all could've been lost. ] She started using her power to finish the job. She was going to kill our parents. And Isaac and Allison and Stiles. They were there trying to get them out.