Derek saw the fangs and tensed. That wasn't as a good sign. Part of him was considering killing him now, getting rid of the creature before it got worse, especially with his ability. His hand was stayed by the thought of the hunters. He'd hated them for what they did, so how could he do the same without hating himself. Stiles hadn't hurt anyone, not yet and he might never.

"Think about your father. Think about Scott. Focus on something human," Derek advised him as he might someone who had felt the pull of the moon for the first time, "Remember why blood isn't the most important thing to you."