Dean considered, biting at his lip while he worked out what was safe to mention, and what he really shouldn't say. The bit about his mom being crispy crittered by a demon, that was out, the bit about his dad trading his life in for Dean's, that was out, so that ruled out the fucking girly pathetic 'he's all I have left' line.
"When I came here," he said slowly, weighing each word, "I just made a bargain. Kinda. For Sam. So, if he looks at you, and he's got no color in his eyes, just black - shoot first, run like hell or come find me. Fast."