"He's pack. I can't completely mistrust him, either." If Isaac's understanding of just what pack meant was flawed, then it showed right then. To him, pack was just a different word for family. You didn't always like your family, hell, he'd hated all his family members at one point or another and had wished ill upon them, but they were still family. In a way, Isaac was aware that that might not be what pack was, and he watched Derek attentively, waiting to see his reaction and glean more information from them.
Did two make a pack, anyway? Was it that simple? If Peter wasn't pack, then they were a pack of two. A good start, but still one that disheartened Isaac greatly even though he didn't let it show. It was just another reason he worried for Boyd and Erica, even though he had stopped talking about them or asking about them. Every day, it seemed less and less likely that he would see them again, if Derek would even allow them to set foot in Beacon Hills again after abandoning the pack.
Isaac did not miss the hard look Derek was levelling on him. He simply chose to ignore it in favour of the book.
However, Derek's subsequent comment had him perking up visibly. Curiosity always made him light up like that, even curiosity of the morbid sort. Especially curiosity of the morbid sort. "Would that be an upgrade or a downgrade from this?" There was cautious hope in his voice, but he really didn't have expectations either way. Isaac still found the whole werewolf thing to be a great adventure, even with the close brushes with death. It wasn't that he didn't take it seriously. It was just that it was simply easier not to break down and hyperventilate. A very fundamental part of him wanted nothing more from life but to survive. Life had taught him that aspiring to anything more was simply vain and stupid. But the questions came pouring out of him regardless, "Do we get our own rooms? Is it an actual house, with electricity and plumbing? Is it going to be our secret lair?"
Still, Isaac frowned, setting the book down in his lap and snapping it shut with great drama the way he'd seen Derek do before. Isaac bit his tongue just in time to keep the accusations to himself, trading it for more neutral questions, though there was a hint of disappointment in his eyes, "What is she going to help us to do? How is she going to help us at all?"