It was 4 am, and Dean was wide awake.

Sam slept quietly in the hotel bed next to his, mercifully able to tolerate leaving the car for the comfort of a room. He had fallen into the bed almost as soon as they had checked in, his body shaking with fatigue and shock, and Dean had been sitting and staring at him since.

Despite the apparent cessation of any visions, he couldn't shake the feeling that Sam was still in very real danger. That dread, coupled with the fresh memory of Sam's lifeless body, were what kept him from sleep.

There were too many unanswered questions – who or what was trying to possess his brother? Why? And how the hell had Sam gotten those runes on his scalp? Without those answers, they were going in blind. And doing just that had literally killed Sam. They needed more information.

Ignoring a jaw-popping yawn, Dean powered up Sam's laptop and logged on to the hotel's wireless internet connection. He stared blankly at the browser screen for a moment, unsure what to search for, then decided to start with the basics. He typed in demonic possession, runes and hit enter. The page refreshed, the heading informing him that 189,704 results had been found.

"Okay…" he mumbled, trying to get comfortable. "This is going to take a while."

While Dean researched, Sam dreamt.

He stood in a motel room, nauseatingly decorated in Seventies orange and green, watching himself sleep. Dean was sprawled out on the bed closest the door, snoring gently. There was an immense air of Déjà vu to the scene, and a moment later Sam realized he was seeing a hotel room they had already stayed in, two months previously.

As he watched, a small, white snake slithered across the floor towards his sleeping form. Its body trailed off into a tail of smoke that whispered after it over the carpet. When it reached the bed the entire snake dispersed into ether and flowed up the dangling coverlet before rematerializing next the pillow.

It opened its mouth and long fangs were exposed, a thick droplet of blood forming on the end of each. He stood rooted, frozen, as the snake reared back, its eyes flashing, and lunged at the back of his sleeping head.

Sam lurched up in his bed, hands flying to the back of his head as he scrambled away from his pillow. He was frighteningly disoriented for a moment, until his brother's questioning voice registered and he realized where he was.

"Sam? You okay?" Dean was moving toward him, looking grim and concerned.

"Dean," he gasped, "I know how I got the tattoos."

Dean looked momentarily perplexed.

"What? How?"

"I was dreaming," Sam said, and Dean's face fell a little.

"A vision?"

"Yeah, but this time it's a good thing… sorta…" He rubbed at the back of his head, unnerved . "I saw us, sleeping in a really crappy hotel room, and this white snake was in the room with us. It wasn't entirely corporeal, it was kind of… smoky. It had blood on its fangs and it bit the back of my head."

"A snake?" Dean asked, staring intently,

"Yeah…"

Dean got up and retrieved the laptop, wordlessly scrolling back a few pages on the browser.

"What is it?" Sam asked, a little annoyed at being left in the dark.

"I think I know what we're dealing with now." Dean said, turning the screen towards Sam.

"A djinni?"

"They usually take the form of a mist or smoke, but they can take on physical form – usually a snake. They're generally invisible to humans, but they're capable of possessing them. They show up predominantly in Middle Eastern cultures, but there're mentions of them in Norse mythology as well."

"Does it say how to stop it?"

Dean sighed and turned the screen towards himself again.

"Not really. It mentions that plucking three hairs from an all black cat with a white-tipped tail, burning them, and inhaling the smoke will dispel a djinni from a possessed person's body, but what are the chances of finding a cat like that?"

"Not good," Sam agreed.

"It sounds like it tattooed you with its own blood – many cultures believe that blooding something will claim it for their own, you know, like a 'property of' kind of thing."

"Great." Sam sighed, "I'll probably get some demonic version of Hepatitis from the little fucker."

Dean chuckled.

"Better that than demonic crabs."

Sam blinked, an involuntary picture forming in his mind, then grimaced in disgust. One hand drifted to the base of his skull again, scratching lightly.

"Stop that." Dean admonished, pulling his arm away. "You'll get that burn infected with your grubby fingernails."

Sam froze, his eyes narrowing in confusion before his hand shot back up to his hair.

"Damn it, Sam, cut it out!"

"No, wait – Dean…" Sam looked suddenly demoralized.

"What?" Dean snapped impatiently.

"The burn, it doesn't hurt. I mean, I think it's gone."

"Gone?"

Dean pushed his brother's head down and pulled the wall lamp towards them. He gingerly brushed the hair away from the base of Sam's skull. To his dismay, he saw that where there had been a angry patch of blistered skin, there was now delicate looking fresh scar tissue, pink and smooth except for the faint returning blush of the Kenaz rune.

Neither of them slept any more that night, sobered by the knowledge that the rune was reforming. Sam had withdrawn after Dean broke the news to him, and now he sat against the headboard, looking tense and jittery as morning sun streamed through the blinds.

Dean was still desperately researching, trying to find a loophole, an escape - any way out of this that didn't involve some unholy creature wearing Sammy's skin like a Halloween costume.

It was strange to be the one doing the geek thing. That was normally Sam's shtick, but Dean had a suspicion that his little brother was too scared to do much of anything right now. He was aware of the desperate looks Sam shot his way when he thought he wasn't looking, and Dean wished fervently that there were some way to reassure him.

Get this thing to leave him alone – that'll reassure us BOTH.

Dean choked down a curse and forced himself to release the fists he'd unconsciously formed. He needed to stay calm, for Sam's sake.

He had no sooner finished the thought when Sam gave a strangled gasp from the bed and jerked once.

Dean recognized the glazed, empty look of a vision immediately, and his heart sank. Apparently the brief reprieve was over and Sam was once again a human lightning rod for every painful, violent memory that echoed beneath the surface of his surroundings.

Unwilling to let his brother suffer, Dean lifted him swiftly into a fireman's hold and carried his unresponsive form outside to the Impala. He didn't understand why it seemed to shield Sam from the visions, but right now, he didn't care why. He only cared that it did.

A/N: Another slightly short chapter, but I have a seriously messed up shoulder right now and typing is a tedious and uncomfortable process. Fortunately for you, the plot bunnies threatened me with further bodily harm if I didn't post. :)