Castiel's recovery was not as complete as either he or Dean had hoped. He was better, of course. He certainly wasn't as broken and helpless as he had been before. But it wasn't perfect. There were moments that only Dean noticed, moments that were tearing Dean apart.
Purgatory was affecting Cas. Dean assumed it had to do with his being an angel. In every other realm, angels were the greatest and mightiest of creatures, but this was different.
He was afraid, Dean could tell. Anyone would be, in this situation, but for Cas it was strange. Like when they first landed here. Normal, sane Castiel would have never left Dean's side, but it was clear that version of the angel wasn't fully there. Surrounded by danger, his wings had been moving faster than his mind could. He had panicked, and Dean couldn't blame him for that. He could only worry.
It had taken Dean about an hour to find Cas. Another had passed before he had calmed the angel down and assured him of just how little he cared that Cas had left him behind. Dean knew he could handle Purgatory, but of his friend he wasn't so sure.
Dean rarely had time to rest. His time was spent fighting, hunting, killing. Sometimes, though, they would sit quietly, having found a quiet spot out of the way of the monsters. They would huddle together for warmth under the cold, starless sky.
Occasionally, only occasionally, they would break the silence.
"These... these insects. Why are there so many insects?" Castiel would say thoughtfully, gesturing at the empty air.
Dean never responded. He only shrugged, pulled the angel closer and said "Go to sleep, Cas."
Once he said "I thought you liked insects."
After a moment Cas murmured, "Not these. They are... loud. And there are too many of them."
One morning (or what felt like morning, but they could never be sure) Dean knew something was amiss before he even opened his eyes. It was surprising that he had slept at all. Dean's nights were usually spent watching for movement in the dark while Cas slept fitfully at his side. But tonight, for some reason he had dozed off. And now he was paying the price: Cas was gone.
Dean forced himself to stop the pointless, impotent whirring of the gears in his mind. Killing himself with worry would fix nothing. Besides, Cas couldn't be far.
He pulled himself to his feet, gripping the makeshift spear in his hand, and set off into the twilit woods.
He opened his mouth to call out, but quickly shut it. That would only draw the monsters to him.
He told himself again, Cas could not be far. And anyway, he could take care of himself. Probably.
Suddenly, Dean was on the ground. It took him a moment to look past the numbing pain of his face pressed against the dirt, but once he did he could feel claws digging into his back. Wet, hot breath crawled over his skin. He bristled.
Hellhound.
Dean craned his neck and could see the beast standing on top of him. On Earth they were invisible, but here their horrible, twisted faces were as solid as Dean's own flesh.
It was small, so maybe he could take it. If he weren't pinned to the ground.
In one movement that was less swift than he'd hoped, Dean rolled over, feeling the claws tear through his skin. Suddenly he was staring into the eyes of the creature. Its breath assaulted his nose and mouth, and he choked.
The hellhound's slimy black paws were planted on either side of Dean, effectively trapping him. He wouldn't escape without a fight, unless he could slip out backward And anyway, it was faster than him. Trying to get out would be futile. With no other options, Dean hauled off and punched it in the nose.
That actually worked better than he expected. The hound's jaw snapped shut with surprise, and it recoiled. It seemed, for a moment, distracted from its prey.
Of course, as soon as that moment passed, Dean would have a hungry, pissed off hellhound on top of him.
Dean seized the opportunity. He swung his legs up and kicked hard into the hellhound's chest. It stumbled back and collapsed a few feet away. Freed, he scrambled back away from the monster.
But it didn't last very long. As Dean pulled himself off the ground he could see the hound standing up. It crouched down, ready to pounce. Suddenly it was airborne, teeth bared, claws outstretched, and Dean was slammed against a tree.
He could feel the rough bark digging into the tattered skin of his shoulder blades. His arms were pinned to his sides.
The creature's sharp teeth snapped inches away from Dean's face. In seconds, they would sink into his throat.
Suddenly, the hellhound let out a painful yelp. With an awful "shlup" sound, its head slid off its body. The headless remains shuddered and slumped over, and Dean pushed it to the ground. He stared up into an ashen face and watery blue eyes.
There were probably more hellhounds, but Dean found his focus glued to those two shining blue pools. They were wide and full of horror, unmoving from the hellhound carcass at Castiel's feet.
"Th- thanks, Cas," Dean faltered, pulling himself to his feet. The other man said nothing. "Hey, come on, Cas. It's okay. It's dead." He tried to make his voice sound gentle and soothing, but Cas flinched at the last word.
"I- he was coming for me," he said. "That's why he was here. But," Cas swallowed thickly. "I killed him. It's fine. You're fine."
As he spoke the words Dean worried Cas might be sick. His eyes were still stuck to the headless remains and the black blood staining his hands.
Finally, Castiel turned to Dean. The spark of fear left his eyes and his face sobered. "He was here because of me. I heard him early this morning, circling us. He sensed me."
"Well, you could have woken me up. We could have hunted this thing together. Dammit, Cas-"
"No. No, it was my fault. It was-" Dean watched as Cas forced his ragged breathing to still. "I brought him here. He hurt you."
He froze for a second. In the silence, Dean heard a growl float into the clearing from the trees. Cas grabbed the machete.
"Cas, I'm fine," Dean said. "We're fine. We're gonna be fine. Just, please-"
Another growl sounded somewhere in the forest.
"Stay here, Cas. Stay with me."
Nearby, a branch snapped on the forest floor. The creatures were getting closer.
"Dean, they're here." Cas's eyes were wide, but he brandished the blade steadily.
Dean stooped to pick up the spear from where it had fallen. He knew it was true. "Cas, we'll be fine. Just... please. Stay."
He turned around, and the angel was gone.