Derek gasped when Stiles hit Peter, but between that and Stiles manhandling him he managed to shake enough of his shock off that he could at least think a little more clearly. "Yeah, that's - okay. Peter, give me your wand."
"Did you really think that was going to work, Derek?" Peter asked, clutching a bloody nose. He fired off a curse that hit Derek's shoulder, right over the scar from the bite. It sent fire burning through his veins and pain radiating out, across his chest and down his arm. He grit his teeth and tried to breathe through it.
"Peter - " he bit out, and lurched forward. "Give me your wand. I don't want to hurt you."
"And I don't want to hurt you. But if you give me no choice then I'm afraid I'm going to have to. Nothing personal, Derek, just what needs to be done." Peter smirked up at him and raised his wand. "Now close your eyes, Derek, if you're going to get in my way then I'm going to have to take care of you, but you have Talia's eyes. I couldn't bear to hurt her."