Dean's heart leaps as Derek tenses, clearly on to something, only to feel it sink like a weight when Derek turns. It's all over his face, and Dean doesn't need to hear the word blood to take off at a dead run, because of course, of course Castiel couldn't make it in this place ten goddamn minutes without getting into trouble.

Behind him, he's aware that someone is calling out, either to him or to Stiles, but Dean doesn't care and he doesn't stop, rounding the next corner hard enough to send gravel flying when he skids to a halt. At the far end of the alley, two men are holding a slighter one against the wall, a meaty hand pulled back to deliver cruel, backhanded slap, and Dean doesn't hesitate.

The knife at his belt is gone, flying on a silent path that ends with an abrupt squealch. Ignoring the man's bellow of pain as he clutches his skewered hand, Dean pulls the tommy gun from his belt and fires a quick volley into the air, the sound thunderous between the dense alley walls.

"Let go of him and get out of here," Dean snarls, "Before I pump you both full of lead."