Sam's breath whistled gently through his interlocked fingers, tickling the fine hairs as it wove its way through them like a miniature gale through mountain valleys. His eyes were caught in a stare as he gazed at his brother's pinched features. It had been almost two days, and Dean still hadn't so much as twitched.

Sam didn't know exactly how long he had spent in a coma after the Trials, but he was beginning to understand his brother's desperation. If it would help, Sam didn't think he'd need as much convincing as he should to help trick Dean into letting Cas possess him.

But that wouldn't help. Nothing would. Sam was helpless, useless, spending hour after hour losing a staring contest with a brother whose eyes he legitimately might never see again.

He heard the door open behind him, but the sudden cacophony of old hinges and squeaking boots didn't so much as make him blink.

"Hey Cas," he said, his voice sounding as dead as Dean looked.

"Anything?"

"No change."

He felt Cas take the seat beside him, scooting it closer as he resumed his vigil.

"Anything on angel radio?" Sam asked, not really caring about the answer. It was a mess out there and he had to find a way to clean it up, and right now, he'd really rather just count dust motes.

"Nothing. If any angels on Earth survived the slaughter, they're wisely staying quiet. As for those who chose to follow Metatron – X, they're either dead or have nothing to say."

"Least Metatron's not hunting you."

"Yes. At least there's that."

"Could he find the Bunker?"

"Not unless someone showed him to the door. It's impeccably warded."

"Then how did Cain find it?" Sam asked. The question had been gnawing at him since he'd slowed down enough to think of the recent events. "For that matter, why did he even show up with Dean like that?"

"What do you mean?"

Sam tore his eyes from Dean's pale features and turned to Cas. "Dean told me part of the deal with him getting the Mark in the first place was that some day Cain would show up and ask Dean to kill him. Judging by what we know of Cain, he doesn't strike me as the kind of guy who'd throw that away. Dean was his only chance at death. Or whatever happens to demons when they die."

"Perhaps he realised Dean had to be stopped."

"Why, though? Cain lived with the Mark for centuries. If he could do it, so could Dean. Why would he hand over his one chance at peace?"

Cas raised his eyebrows thoughtfully as he picked at a loose thread on the blanket covering Dean. "That's a good question. If we ever see him again we should ask."

"That's another thing that worries me. What if we do see him again?"

Cas nodded, his eyes turning to Dean's face. "It's been almost two days."

"Yeah." As if Sam wasn't counting the hours.

"You mentioned the Bunker had a hospital section?"

"We're not moving him. He loves his room."

"No, of course not. But he is weakening. We should probably see if there are any IV's or ... something."

"Why can't you just heal him?"

A pause.

"Because there's nothing to heal."

Sam gave the angel a look. "What?" he asked flatly.

"When I heal a human," Cas explained patiently, "I simply magnify their innate healing abilities. I add to what's already there, waiting. Speed things up. As long as their soul has the energy for it, I can heal almost any usual ailment with just a touch." Cas raised two fingers in the air, pressing them to an imaginary forehead. "With Dean, his soul is too weak to sustain such an intrusion. Healing the contusions on his neck took the last of his strength."

"What about your Grace? Can't you just use that energy?"

"Not for a wound like this. Only souls can heals souls, and I don't have one."

"I can't take this, Cas," Sam confessed softly after a long pause.

"I know," he answered quietly.

"What if he –" Sam couldn't bring himself to finish the sentence.

"I know."

"How do we even know the Mark is contained right?" he exclaimed, exasperation and worry colouring his tone.

Cas thought a moment before answering. "I suppose we don't. We only have Death's word. We'll just have to trust in it."

Sam huffed. Trusting in the Grim Reaper's promise. God, his life was weird.

"What if –" Sam's voice caught and he started again, blinking back the unwanted moisture in his eyes. "What if I did it wrong? What if I messed up? The lines, they had to be so precise," he said, gesturing to the two brands on Dean's arm. "What if –"

"Sam," Cas interjected firmly. He waited for Sam to meet his gaze before continuing. "You've done everything you could, as well as humanly possible. And that means something, coming from an angel. You need to just ... be patient. Try to keep calm. Worrying isn't going to help anyone."

Sam nodded. "I know. I know."

He hung his head against the weight of it all. He felt Cas's hand grip his shoulder in solidarity. At least he didn't have to bear this burden alone.

"I'm glad you're here, Cas."

Sam didn't see the angel's small, touched smile lift his features. And neither noticed as the single tear escape Dean's left eye and trickle slowly down to disappear into his hairline.