No one would have had to know. Once he got a good taste, Sam could pull that demon out of Sunshine so fast that she wouldn't even realize what hit her. No more failed exorcisms. No more worries about rock salt and holy water. This was right. Sam needed his abilities to take all those other demons on and now, with the two of them locked away inside of his motel room, Sam had the perfect opportunity to take what was already his. Demon blood. Every precious drop, every single bit of that dark, coppery liquid tainted with Hell that fueled his abilities like nothing else. Just a taste. A little taste. That's all he needed. Sam stared at her bloody arm, taking little to no concern toward the wide eyed look he'd been given in return. Something about him having black eyes? Huh. So much blood. All going to waste...
Every single part of his body screamed for him to jump forward. Sam could already see the scene playing out in his head - his large arms pinning the demon down against the sink, holding it in place as he bit down onto her arm and sucked the blood right on down. Warm, delicious - it was power. And there was truly nothing in the world that Sam Winchester craved more than that, deep down. Hands clenched into tight fists at his sides, Sam only barely managed to resist making that scenario come to life. He had been close to it. Sam honestly had been. The chance to taste demon blood again, the idea that he'd finally be able to do some damage to those things invading the city - it was more than enough motivation for one with an addiction as strong as his own to want to act out.
But he didn't. Because Sam, flawed as he was, knew better than that. He had learned the hard way what happened when he dabbled with demon blood. Both he and Ruby had. And if he wanted to ever fully right his wrong, he needed to stay far, far away. Fortunately for him, with Sunshine covering the wound with a wash cloth, Sam was able to break free from that starving gaze he'd fixed upon her arm. Blinking, Sam stumbled back a few paces, his shoulders hitting the wall behind him hard. "I -" He brought a hand up and ran it over his mouth. He needed holy water. Rock salt. Something. But, then again, he already had plenty of that littered along the entrances. How had she gotten in to begin with?
The demons are immune, Sam reminded himself. Either that or what Castiel had been saying was true. God, he was so confused. With his mind purely set on: blood, blood, blood? It made things a lot less clear than they had been a few moments before.
"Your eyes," Sam started, finally managing to process the words that had escaped Sunhine's mouth earlier. "They're black too."