A/N: This is nearly it! Just in time for the new season to start and everything that happens here to look entirely ludicrous in retrospect. I hope you've all enjoyed reading!
Sam wasn't expecting a knock at the bunker door. More than that, he wasn't really expecting Hannah to return.
"Cain, at your service," she said primly, pushing the man into the bunker and walking away before Sam could say anything.
"Hi," Sam said to the man. "Are you Cain?"
"That's what the angel said, isn't it? Why did she bring me here?"
"My brother. You gave him the Mark and now he's a demon. I want to know how to reverse it."
"How to cure a demon? I don't know that."
Sam shook his head impatiently. "I want to know how to get rid of the Mark."
Cain frowned. "Do you really think I would still have it if I knew how to get rid of it?"
Sam scoffed. "Would you have been able to give my brother the Mark if you hadn't done it before? Wouldn't I have heard of Marked demons running around if there were any?"
Cain nodded grudgingly. "You've got a brain, at least. That's good But the rest of the people who I Marked were killed by angels long ago. The Mark is permanent."
Sam set his jaw. "I don't believe you. I don't think you would have been so willing to give Dean the Mark if there was no way to take it back."
"Oh, don't worry. There's a way to take it back. Dean just won't be able to go through with it, now that he's a demon."
"I can make him human again," Sam said eagerly. "Then he'll be able to go through with it, right?"
Cain shrugged. "It's possible, I suppose."
The hunter grinned. "So what do we have to do?"
It didn't take Shamsiel long to find Castiel. Everyone in Heaven knew where he was and what he was doing. He was surprised by how little they seemed to care.
"Then I'll find someone more willing," Castiel's charge growled as Shamsiel appeared next to him.
It took the other angel a long time to notice him, but when he did…
Shamsiel nearly fainted – Cas actually did. The frequencies both beings existed on – the frequency, singular, something Shamsiel had never realised could happen – vibrated with the combined force of both the angels' weight.
"Cas?" The demon asked. "What…" He turned around and saw Shamsiel standing behind him. His grip on the First Blade tightened. "What have you done to him?!"
"Nothing." Shamsiel swayed. "It's just…" The frequency stabilised, and he walked towards his Partner.
Cas sat up and rubbed his head. "What happened?"
Shamsiel sat down next to him. "We exist on the same frequency. How is that possible? Could it – Hannah can't be right."
"Hannah can't be right about what?" Dean growled. "What's that bitch got to do with anything?"
"She said that we were angelic partners, but that can't be true. There's no such thing."
Cas sighed. "Hannah is correct. We are angelic partners."
"But what does that mean?" Dean asked.
"It means that Hannah has found a way to keep me alive."
"Dean must want to be saved, and he must be saved by an angel. If he does not truly want to be saved, he will be killed by the angel."
Sam sighed. "How do we get him to want to be saved?"
Cain shrugged. "Not my problem. Maybe you should focus on making him human first."
Castiel appeared in front of Sam. "What did you say to Hannah?"
Sam blinked in surprise. "We made a deal. I know how to save Dean. And we need you to do it – and to be fully angelic to do it."
Cas looked from Cain to Sam and back again. "Can another angel not do what you need?"
"Would they?"
"If I asked them to, they would." The idea still baffled him.
"And would you ask?"
Cas sighed.
"Please, Cas. You deserve this. So does Dean."
Cain coughed. "Both parties need to be entirely willing or it won't work. In fact, it could kill them both."
"I don't know that I can do this," Cas said, before disappearing back off to see Dean.
Shamsiel didn't like Dean. He didn't like demons in a general sense, but he specifically disliked this one.
"Stay away from Cas," Dean said for the twentieth time, swinging that Blade around like it was a toy.
"He currently appears to be doing my job for me," Shamsiel said dryly. "But I'm here to help him. Hannah said that he didn't want to be saved."
"What? What does he need to be saved from?"
"Dying. Castiel doesn't want to be angelic anymore."
Dean scoffed. "He probably thinks he doesn't deserve it anymore. As if you guys are some higher life form that can do no wrong."
"And that's ridiculous, is it?"
Dean rolled his eyes. "Sorry. I forgot that you were an angel. You probably believe he doesn't deserve to be an angel."
Shamsiel shook his head. "I don't think the form his existence takes matters. I just think that it's important that he exists."
"Why? What do you think makes him worth it?" Dean desperately wanted to know what the angels really thought of Cas; what the angel's life was like with his 'real' family.
"There is no question of 'worth', Dean Winchester. All beings should be allowed to live, simply by virtue of their being. Castiel doesn't have to do anything to deserve my help, although I do sometimes ponder whether it is cruelty to keep those who wish for death alive."
Dean frowned. "Then why are you fighting to keep him alive when he doesn't want to be?"
Shamsiel paused. He disliked this demon, but he had heard some of his story from the few angels he spoke with. He knew that Dean Winchester was not currently happy with his own existence, and he knew that the once-Righteous Man deserved to live just as much as the next person. He looked the creature in the eyes. "I used to be one of those people who didn't want to live. Now I'm not, and I'm very glad that my friends helped me to stay alive."
Dean looked away, clearly catching the angel's train of thought.
A flutter of wings knocked them both out of their own thoughts.
"Dean," Cas said, his voice shaky as he stumbled forwards. "Dean…"
The demon ran towards the angel. "Cas? Cas, look at me. What's wrong?"
"He's losing his borrowed Grace," Shamsiel said. "It's leaving him faster than it was before. We have to get him back to Heaven. We need Hannah to explain how the spell works."
"How long does he have?"
Shamsiel looked uncomfortable. "Not long enough. He's too weak to travel there himself, and my wings aren't strong enough to hold us both – they were injured when I Fell."
"Can you not just try anyway?" Dean asked.
"If I drop him, he'll be lost between dimensions. I can't take the risk."
"There's no other way! Just take him, dammit!"
"Dean…" Castiel whispered. "I need to…"
Dean dropped to his knees next to his friend. "What?"
"Do you want to live?"
"That's kinda besides the point right now, Cas."
The angel grabbed onto Dean's sleeve. "No. Tell me, Dean: do you want to live?"
Dean looked over at Shamsiel. They locked gazes, and the angel nodded at him.
"You deserve to try," Shamsiel said.
"Okay. Yeah, Cas. I want to live."
The angel's face relaxed into a smile. "Good. I know how to work the spell."