She couldn't actually promise that. He knew it was out of her hands just as it was in a way out of his. He was a monster, he had fangs that would do some serious damage.
But Kate was a driving force in his life. For better or worse, she wanted to be with him. He could control his blood lust, and it was in her best interest, as well as his, if he put the events of the past week or so behind him. He hadn't hurt anyone, he wasn't going to hurt anyone now.
He would die before he'd hurt her. He looked up to meet her eyes, gave a small nod. He trusted her. That was never the question. It was himself he didn't entirely trust.