Author's Notes: This was a request someone made. They asked for Dean/Cas based on the song "Undisclosed Desires" by Muse. I ended up listening to it about 67 times or something while I wrote this. Also, Cas is a bit of a perv.

Warnings: Semi-graphic depictions of sex and some voyeurism.

While there was a great deal Castiel found frustrating about being weakened and trapped on Earth, one of the most troublesome was that all his allies were human and thus had needs he didn't. Sleep was particularly annoying but he could do nothing about it. Dean, Sam, and Bobby all needed rest if they were going to be any help to him at all.

He coped with this human fallibility by using the time while they slept to search for his father. While he followed claims of miracles around the world in the desperate hope one of them would be his father, he waited for his phone to ring so that he could once again focus on killing his fallen brother. The world was falling further and further under Lucifer's control. It was easier to find disasters than miracles. Castiel was impatient to stop Lucifer before there was nothing left to save.

In Bagladesh there were reports of a faith healer who was not just another con artist. The man was actually charlatan, but he found a lead, a good lead, on an ancient text written by demons on Lucifer. Demons were looking for it as well and that meant it had to be genuine. He couldn't let sleep interfere when it was something this important.

He knew where Dean was, he knew that if he called right now – it was 3 am in Butte, Montana – he would just get a sleepy voice and annoyed Dean who would swear and tell him to call back later. Yet, he was not limited to human ways of communication. What he had in mind was quicker and it would allow Dean to stay sleeping while they talked.

When he appeared in Dean's dream he found himself in a cheap, nondescript hotel room, the typical kind Dean stayed in. He expected his presence to be acknowledged right away. Dean was very aware when his dreams were invaded, but tonight Dean's unconscious self was occupied. Shock kept Castiel from saying anything to announce himself.

Dean's dreaming self had him, a dream representation of him, pinned to a wall and they were locked in a deep, open mouthed kiss. Castiel stared, unable to look away as the kiss continued, their tongues dueling for dominance but it was clear Dean was the one in control. The dream version of him looked identical to him, except for the way he kissed Dean back, clutching at the back of Dean's shirt. The wanton expression and naked desire in his face was not an expression Castiel had ever made purposefully.

"You got no fuckin' clue, do you?" Dean whispered furiously when he tore his mouth away from the dream Casitel's. He pressed his mouth under his dream self's ear, grinding a thigh between the dream Castiel's legs hard enough to make him cry out in shocked pleasure.

Castiel flushed deeply hearing that sound from his own mouth, or at least a facsimile of his own mouth. In his brief encounter with the prostitute Chastity, he had made a similar if more subdued sound before he was scared her. How did Dean know how he would sound? Why was Dean dreaming of how he would sound? Why was Dean dreaming of him in a clearly sexual manner?

"No. Fuckin'. Clue." Dean punctuated each word by grinding harder against the dream Castiel. "You got no idea what I'm gonna do to you, what I want to do to you. I'm gonna break you, Cas, gonna make you fall apart."

The dream image of him shuddered and seemed to melt against Dean, accepting the somewhat harsh way Dean was moving against him as if he wanted it. When Dean stepped away from his dream self, who let out a cry of disappointment, making it clear how much he wanted it.

Dean only chuckled roughly and began to undo the snap of his jeans, "Knees, Cas, get on 'em."

His dream self dropped immediately and stared up at Dean, eyes wide and mouth open as he drew in shaking, deep, expectant breaths.

Castiel took himself far away from Dean's dream when he realized what was going to happen. No matter what Dean thought, he wasn't ignorant of sex and the things humans did with one another. Not only had he been on Earth a long time but he knew how most of his father's creations procreated. What he was going to do in Dean's dream had nothing to do with procreation and he blushed violently at the thought.

An even more terrible realization washed over him as his own imagination took over. He wanted to watch, to see what Dean planned to do to his dream self. He knew he tended to be curious, but wanting to see that, something so blatantly sexual and undoubtedly graphic between him and Dean…

He shuddered, even though it was blazingly hot in the outback. Dean had been right in the dream. Castiel had no idea that Dean wanted him like that. He had never even considered it. He never would have except, now he had seen that dream and it was circling around in his mind, bring up more questions, more confusion and even more frustration.

Sleep, Castiel decided as he forced the dream out of his mind, was quite frankly a human experience he wanted nothing more to do with and from now on he would wait until Dean was awake to deal with him.

But he would always wonder what else Dean was keeping from him in his dreams.

"Alright, man, what's up with you?" Dean asked.

From his place in a corner of the hotel room, Castiel raised an eyebrow and tilted his head slightly. "Nothing is up with me," he said, a note of uncertainty in his voice.

Two weeks had passed since he had accidentally seen Dean's sexual dream about him. In that time, they had gone from Montana to a town just outside New York City. The book they were hunting was supposed to be in a museum there. It was proving difficult to find just which museum and where it was being kept so he could take it. He had given no outward indications of what he had seen, nor that he knew Dean desired him.

"Yeah? Then why do you keep acting weird." Dean paused, making a face, "Weirder than normal for you."

"How I behave is not what you're used to, but that doesn't mean it is weird," he said.

"Dude, I know how you behave. You're stiffer than a board, you get in my face with that commanding doom voice and you don't deal with Sam unless you have to. Now you're callin' him instead of me and you don't stand near me unless you have to. Also, the staring thing is getting really creepy."

Castiel blinked. He hadn't been aware he'd been doing any of those things.

Dean rolled his eyes. "Man, what? Are you pissed at me or something? Did I get your trench coat in a twist? You gotta tell me because I don't have a clue."

He looked away, that phrase triggering his memory of the dream. Unconsciously he licked his lips, as if he had been the one Dean had kissed and not some vision of himself created by Dean's subconscious.

"It is nothing important," he said to appease Dean. He would have to adjust his behavior to make sure Dean didn't notice anything else wrong with him. Or, perhaps, stop coming around so much. He could easily communicate by phone and he still had to find his father. That would easily solve the problem until he was able to act normally around Dean.

"Right, right." Dean got up from where he sat on the edge of one of the beds and closed some of the distance between them. "But it's got to be somethin' because you can't say nothing is nothing."

"It doesn't matter, Dean." There was nowhere for Castiel to go, trapped in a corner like he was, unless he flew away. That would certainly alert Dean that something was wrong. Dealing with these complicated human emotions was also one of the downsides to his allies being human.

Dean frowned a bit and crossed his arms, "You sure?"

He nodded. "Yes, I am sure."

"'Cause I don't think you are," Dean said, taking a few more steps forward, arms still crossed. "You don't look sure at all, Cas. You look like something's on your mind."

"It is the end of the world," he said calmly. "There is a lot to think about."

"The end of the world make you blush?"

Castiel blinked and reached up, touching his own cheek as if he expected his fingers to come away stained pink. He hadn't been aware that he had.

"Yeah, kinda sucks when the body's all yours doesn't it?"

He glared a little at Dean's accusatory tone. Castiel understood the sacrifice Jimmy had made for him and never forgot that the body he now wore was his and his alone.

"Come on, Cas, if I fucked up, I'm sorry alright?" Dean moved in to his personal space, trying to catch his eyes so that he couldn't look away.

"I saw your dreams," he said quietly when he met Dean's eyes.

He could see it right now, playing in the back of his mind, how Dean had kissed his dream self and how his dream self had responded, how eager and how much he enjoyed it. For the past weeks, a voice in the back of his mind wondered if he would enjoy it too. He had been ignoring that voice or at least trying but like the dream every time he had looked at Dean it had spoken up and the dream would play in his mind.

"What?"

He swallowed and hesitated before he leaned in to kiss Dean. It was not like the kiss he had witnessed, it was more delicate, uncertain. Dean's lips were wider than Chastity's, but warm and surprisingly soft as they pressed against his.

"Shit, Cas," Dean whispered, then slid a hand into his hair and pulled him into a harder, more forceful kiss.

He shuddered just like his dream self had and realized that perhaps Dean's dream had revealed more to him than he thought. Just like his dream self, he let Dean push him back into the wall and pin him there. The press of Dean's body against his was strange, but it made him feel warm and he pressed even more into him, strangely eager to explore this sensation.

"You gotta stop me," Dean begged, moving his mouth over Castiel's jaw. "I can't do this to you for real. I'm going to wreck you. Don't let me."

Castiel was confused. Dean wanted him, but didn't? But, perhaps he should listen and stop Dean. Sins of the flesh were not something angels, even one like him, indulged in. Yet, as fearful as he was, he found himself wanting, just like he had in the dream.

He clutched at Dean. "Show me," he said, somewhat breathlessly.

"Don't," Dean repeated, as if he was in pain. He gripped the back of Castiel's head tightly, short nails digging in for a moment before he released him. "Don't. You don't know what you're asking."

"I know," Castiel said, though that wasn't actually true. He really wasn't sure what he was asking, but he wanted to know. The desire for knowledge, the desire for Dean took away any hesitance he had. He wanted and that feeling was new and so strong.

Dean groaned, a broken sound and kissed him again. He ran the tip of his tongue over his lips and Castiel trembled at the heat and the wetness. He groaned, in wonder and confused desire. Dean pulled him closer and pressed his tongue into his mouth. Castiel kissed him back, awkward, inexperienced but quickly he learned how to fit his lips against Dean's, how to move his tongue around Dean's, how good it could be when they had sorted this kiss out.

With his head swimming, Castiel turned control over to Dean, let him guide him away from the wall, shoving his jacket and suit jacket from his shoulders to the floor. Dean tugged roughly on his tie, jerking it free before pulling his shirt open.

"Jesus, Cas," Dean whispered hotly against his neck.

The blasphemy shocked a gasp from him, but it didn't deter Dean in the least. He pushed him down onto the bed, quickly pulled his shirt over his head and pinned him down to the scratchy, threadbare comforter. But the warmth of Dean's chest pressed into his quickly distracted him from the itch against his back.

Dean's mouth stayed on his neck, nipping and sucking as he reached a hand between them and dealt with the snaps and buttons of his slacks. He drew in a deep shocked breath at how it felt to have Dean's hand around him. He understood, with almost painful clarity, why humans enjoyed this so much. The pleasure was liked fire, burning through his blood, carried through his whole body with every hard beat of his heart.

The details began to blur, but he knew that he reached out to touch Dean, trace the peaks and valleys of his back, chest and hips. He heard Dean whisper his name and ask him if he liked it, if he wanted it. He felt their legs tangle together as they kissed in one long, seemingly endless duel of lips, teeth and tongue.

It was an aching shock that made his hips twist when he felt Dean's fingers press against and push into him, slick with gun oil and seeming burning hot. It didn't discourage Dean who kept going, pressing his fingers deeper and hard until he felt his body moving with Dean's finger. Then they were gone, replaced by Dean's cock and Castiel was lost after that.

Feelings, needs, and wants competed in his mind and through his body as he clutched blindly at Dean, looking for him to anchor him through this alien experience. It consumed him, burned him up from the inside until a sharp, violent burst and he felt rapture. He was dimly aware of Dean calling out his name, dimly aware of his weight on top of him and of being exhausted.

That certain explained things.