What if Sam's immunity kicked in a little sooner?

Sam, Dean and Ruby ran into the study and closed the doors. They threw devil's shoestring in front of the door to keep the hell hounds out. Sam and Ruby continued to hold the door while Dean ran over to the window and shoestringed the window.

"Give me the knife," Ruby said to Sam.

"What?"

"Maybe I can fight it off."

Sam hesitated for a moment and then realized that she had a better chance of fighting off the Hell Hound then he did. After all, she could see it. He lifted up the knife and started to hand it to her when Dean yelled, "Sam, don't."

Sam stopped even though he couldn't imagine why Dean didn't want him to give the knife to Ruby. Sure he didn't trust her, but he was out of time with no options now. What did it matter what they did?

"That's not Ruby," Dean said answering Sam's unvoiced question.

Sam immediately lifted the knife up to stab her, but she stepped back and went to fling him into the wall with her demonic power. She managed to knock the knife out of his hand, but Sam himself didn't move.

"Back," she said, but again nothing happened.

Dean stepped forward to grab the knife and stab her. She flung her hand against him and he went back onto the table behind him.

"Lillith?" Dean asked.

"That's right," Lillith sing-songed.

Sam bent over to pick up the knife. Lillith ran over to the door and opened it. The invisible Hell Hound brushed past Sam and went to attack Dean.

"Sorry, I can't stay to watch," Lillith said. She didn't exactly feel safe with a human who was immune to her charms. She smoked out of her body and left for somewhere far away.

Sam watched the horror show in front of him. Dean was being torn apart and was screaming. He was rolling over, but Sam couldn't see the hound to stab him. He had no idea where to stab. All too soon, it was too late. Dean was dead, and Sam assumed the Hell Hound had left the building.

He knelt down next to Dean, sobbing. He lifted Dean's body up and cradled him.

"Help!" Dean yelled from the rack. He was hot and in pain. All of that was eclipsed by a single question. "What was wrong with Sam?" He had been immune to a demon. That couldn't be good.

The End