Dean jumped, woken up, when he felt the vibration of his phone in his pocket. Not one to usually ignore a call, even this early in the morning, he barely glanced at the caller I.d. before answering.
"Yeah," he said, plain and simple as that.
"Dean," said the gruff voice he knew so well.
"Cas?" he said in surprise. "Where are you? Are you hurt? What's going on?"
"I'm...fine," said Castiel, "but I have a confession to make."
"Well go on, spit it out; do you know what time it is? I've told you before not to call when I need some sleep."
"Dean," he said, firmly, "this is important."
Dean wondered what could possibly be so important that Cas would call him in the middle of the night. Instantly, he perked up and forced himself to get out of bed. After all, Cas could be in danger...or worse.
"Alright, I'm listening."
"I've lost my grace," said Castiel, "and I've created a terrible mess."
Dean was reminded of the post-apocalyptic version of the future he had been shown by Zachariah once. Castiel being human had been just one of the many elements in the tragedy he'd forced himself to prevent by saying yes to Michael and becoming a vessel. Brief bits of the conversation he'd had with that Castiel came back to him.
("So you're human," he'd said. "Yes," the future Castiel had replied. "Welcome to the club," had been Dean's snide remark to this.)
"Where are you?" he asked, assuming the protective older brotherly tone he'd used with Sam for years. "I'm going to come and get you, and then you're going to tell me everything, alright?"

Dean drove around in the Impala. He was sure that he was near the place where Cas had said he'd be, although it looked unfamiliar.
Suddenly, waiting by the side of the road was a familiar figure. He looked a little dirty and his clothing was a bit rumpled but it was still him; it was still Cas. Dean didn't know whether to go up to him and hug him like that one time in Purgatory or yell at him until he was hoarse. Instead he pulled over near the spot where Castiel was sitting.
In that instant Cas looked up, an expression of clear relief on his face.
"You came," he said, as if he hadn't actually expected Dean to come.
"Of course I did," said Dean, "what did you think; that I was just going to let you die out here, all alone? Now hurry up and get in the car, before I change my mind."
Cas walked over to the Impala and opened the front passenger door. The expression on his face was one of gratitude, although Dean pretended not to notice. Now was not the time for him to be dealing with his rather complicated feelings towards the former angel with which he still had a profound bond in spite of everything they had been through together.
Finally, after a couple minutes of awkward silence, Dean risked a look at his companion. He seemed to be the same as always, on the outside, just as he had been the last time he had become a human. Except this time his face didn't have that sullen, downcast look, the way it had had before. If he wasn't mistaken, for the first time Dean thought he saw what seemed like hope in Castiel's bright blue eyes.
In that instant, Castiel unconsciously held a hand over his stomach, and grimaced slightly.
"Are you alright, Cas?" asked Dean, careful to keep his tone neutral. It was better if Castiel was kept unaware of his feelings...for now.
"I feel strangely hollow inside," admitted Castiel, "it's very uncomfortable."
Dean smiled in spite of himself. Just like before, it would take some time for him to get used to Castiel being human. "It means you're hungry," he explained. "Lucky for you there's a restaurant nearby. We'll talk in there."
It was just his luck that as he said this they passed a large blue sign indicating several restaurants ahead. Minutes later, Dean pulled into the dimly lit parking lot of a 24-hour restaurant. When he and Castiel got out of the car he turned to the former angel and said, "Now let's get you something to eat."
Cas nodded agreeably and they went inside the restaurant. Out of habit Dean looked around suspiciously at the few customers who were already seated; he couldn't be too careful, in case any of them turned out to be demons. As if sensing his angst, Castiel put a hand on Dean's shoulder. The gesture was most likely meant to be reassuring but it still made him tense up slightly.
They sat down at a booth, taking seats that were across from each other. Dean reached over and handed Castiel one of the two menus that had been placed at the table beforehand.
"Go ahead, pick anything you want. This one's on me," he said.
Castiel glanced over the menu for a few minutes, a contemplative look on his face. Then he looked up at Dean, whose gaze was surprisingly calm and almost happy for once.
"Well?" he said, "Did you decide what you want to order yet?"
"Yes," said Castiel, "I think I'll have the pie."
Dean looked at him in surprise. He knew very well that Cas loved hamburgers, not pie. It was an unusual request, especially since Dean was the one who loved pie. He shrugged, trying not to seem as confused as he felt.
"Alright," he said, "if that's what you want."
"I want it," insisted Castiel, "because I know it's your favorite food."
Dean was surprised and a bit touched that Cas had noticed something so trivial about him. He thought he could immediately see what his companion was trying to do.
"You don't have to do this, Cas," he said in an attempt to be convincing.
"And you don't have to provide for my meals but you are," pointed out Castiel, "I was simply trying to return the favor."
Dean glanced at him, a look of appreciation on his face. Castiel doubted that the look would stay once Dean knew of the terrible thing he'd caused.
They sat in silence until their food came. It was only then when, a thin slice of pie in front of him, Dean decided to channel his inner fake FBI agent, the persona he and Sam had both adopted when investigating a case of the supernatural so as not to raise suspicion.
"So tell me something about this situation you've gotten yourself into," he said invitingly. Being able to interrogate someone was just one of the many things of which he'd have to show Cas the ropes if he was going to stick around with the Winchester brothers, in his current human state.
"Well, it's simple," said Cas, around a mouthful of pie, "Metatron removed my grace, and now...I am human."
Dean shook his head. "I can see that," he said, " I was talking about the...mess you said you created."
Instantly, Castiel's face fell. He knew that Dean would not be happy to hear the news that he had possibly betrayed him and Sam, yet again. They were the only friends he'd made so far, and he knew that he would be lost without them. He did his best to look anywhere but at Dean, as if doing so would help him avoid the inevitable truth.
"Cas," said Dean, an unspoken warning in his voice, "I know that look. What happened?"
Castiel sighed and forced himself to look into Dean's green eyes.
"You have to promise you won't be mad," he said, tentatively.
Dean looked worried. "It's that bad, huh?"
Cas nodded, not trusting himself to speak.
"Well, alright then, I'll try."
"I...managed to open the gates of heaven," said Castiel, cautiously, "and in the process many of my brothers and sisters suffered tremendously."
Dean's eyes widened in understanding. "Oh...so all those angels falling; that was you?"
"I'm not proud of what I've done," said Castiel, "and I'm not sure if this is something that can be undone with angel "mojo", as you call it. If I knew a way to fix this, I would. But I'm afraid...until I find a way, I will not be in their favor for causing all this damage."
Dean looked at him sympathetically, and placed a hand over his from across the table.
"Look, don't worry. You're part of Team Free Will now, and Sammy and I will make sure nothing bad happens to you, alright? If anyone tries to lay a finger on you, I'll keep you safe."
Castiel smiled. This was unlike Dean, going out of his way to protect someone other than his brother. He only did so for those he truly cared about, or so Castiel had observed in his time with the Winchester brothers.
"Thank you, Dean," he said, gratefully.
Dean nodded, careful to keep his expression neutral. He meant every word he said, and he was determined to prove this to Castiel. Letting him know this was the best, and safest, way of saying how he truly felt, for now. But he was also afraid that, like almost everyone else who he had let himself care about before, if he ever actually told Castiel how he felt, Cas would eventually be torn from him too.