"Time doesn't permit that sort of mess-a man meeting himself. When such occasions threaten, Time steps aside." – Ray Bradbury, "A Sound of Thunder"
It was five o'clock, or it had been when Castiel's watch stopped, and there was a pounding in his head. The blood on his jacket wasn't his. He wished it were his.
The rest of their regiment had already left or been killed, and more likely the second one. There were no Croatoans around now, at least no living ones, and the sky was streaked with oncoming rain and still the blood stuck to his muddy skin.
It looked enough like human blood- like his blood- but he knew where it came from, vaguely remembered stabbing at the crumpled form of a Croat below him, knew what it meant that he had its blood coating his arms and neck. It would have been ridiculous to say he could feel his blood changing, but Castiel swore he could, swore he could feel the churning and stinging as the infection dipped into him and touched every human organ it found, swore he could feel it swilling up his brain, turning him into a monster.
He had to find Dean.
If he was being completely honest with himself, he really didn't believe Dean or anyone else had a chance in hell of killing Lucifer, but still he had to find Dean. He needed to say goodbye. He needed to ask him for one last favor.
It was five o'clock when Cas pulled himself away from the gory wreckage of what had once been a busy street so he could find Dean and ask him to kill him. Maybe he was nothing compared to what he'd once been, but he refused to become this.
With no map, it took Cas longer than he would have liked to find the garden, and the pounding in his head grew louder and louder. His pulse raced, and even as he began a gruesome metamorphosis into something twisted and terrible, he felt more human than ever.
He finally got to the garden, and still his veins strained and his head ached. It would be so easy to lie down, to get up again as some animal who didn't need to worry about pain and morality. Still, he somehow dragged himself through the entryway, almost to the point of falling over.
For a moment, he didn't see Dean. For a moment, the garden was empty, no Lucifer, no Dean, past, present, or future. And then there he was.
Though Dean had complained about it constantly, Cas had always enjoyed watching him sleep, and while he would dole out excuses about learning human behavior or keeping watch, he actually just liked the sight of Dean's sleeping face. It was the only time when all of it- Sam, the apocalypse, the torture- faded away and he seemed at peace.
He wasn't sleeping now, and when Castiel took in his twisted and still form on the wet grass he had to fight not to fall to his knees. Of course the Devil had won. He always did. Always would.
With the Croatoan virus raging inside of him, Cas took aching step after aching step to get to Dean, and there finally he knelt down, rolled his friend over and checked for a pulse as if he had the shadow of a hope. He'd known this Dean- the now Dean- from the other one for the tense set of his shoulders and the tired lines by his eyes, and for the air of defeat. Still, he knew this Dean better than anyone else there ever was, better even than the angels he had once called family. Knew him for the way he kept his weapons, the sharpness in his voice when Cas brought up his brother, the glint in his eyes when he remembered that he used to believe in hope.
Now it was all gone, and left was just the shell of a man Castiel had once known, and he wouldn't be killing anyone today. "Should've known you'd let me down," Cas said bitterly, and he immediately tried to say something else because he didn't want his last words to Dean to be so cruel, but all he could manage was a dry gasping. He could feel rage and a growl crawling up his throat, could feel himself about to lose it all.
And while he'd hated living as a human, he was sure as hell going to make sure he died as one. Dean had a gun in a holster under his jacket. Cas grabbed for it with shaking fingers and forced it up against his head. He knew enough about luck and life to be sure that wherever he was going, Dean wouldn't be there, so he took one last look down at him. He could've been sleeping.
There was a sound of thunder.