When Sam jumped up and punched Jack, Jack stumbled slightly, but quickly recovered as a hand went to the now slightly sore spot. It wouldn't be sore for long, but that didn't matter. Something was wrong with Sam, and Jack needed to help him.
"Sam. What's going on?" Jack asked, blue eyes wide with concern as he stood up, the mark on his face now bruising. "Sam. Talk to me. Please." Jack pleaded, trying to get to the Winchester in anyway he could. Were Sam's hallucinations getting worse? Jack wasn't sure, but right now, he was more worried than anything else.
If he had to restrain Sam, he would. But he'd rather not if he had any choice in the matter. Currently, Lucifer was no where to be seen, and it was just Sam and Jack.