Dean clutches his forearm in pain as the Mark of Cain burns red. Long-term effects of holding the blade include the longing for it, the painful longing for it.

He sits alone in the bunker staring at himself in his mirror. Sam had gone out on a beer-run and no one had seen Castiel in weeks.

The pain escalates to the point where nothing else can be perceived, and Dean falls his his knees in pain. He hears a sudden noise behind him, and even in his pain-induced state he finds a way to reach for the demon knife and spin around to face his attacker; but the knife falls from his grasp as he sees who it is.

"Castiel." The word escapes his tight lips, sounding like the only word that matters. In a way it is.

"Dean what-" Castiel's words fall flat as his eyes focus on the exposed mark on Dean's arm. Quickly his face becomes angry.

"Cas, before you start, please, you don't understand my situation. We had no choice! I needed to find Abaddon and-"

"Be quiet." The power in his voice silences Dean.

Castiel crosses over to Dean and grabs his hand, pulling his forearm out so he can closely inspect the mark.

"I've only ever heard of it. I've never seen it with my own eyes. So you met him, you met Cain?" Dean only nods. "You met the father of murder, and didn't call me?"

"You weren't really around." His excuse sounds weak.

"You could have gotten yourself killed! Or worse!"

"I-" He wants to explain but the mark starts glowing red again, burning his skin in an unimaginably painful way. "Oh god!"

"Dean what is it why is it burning you?" Cas falls to his knees to be on the same level as Dean.

"It's..." He tries to breath through the pain, clenching his eyes closed tightly. "Longing. For the blade."

"You held it?" His hold on Dean's hand tightens. "You used it?"

"I couldn't help it." Dean finally breaks, dropping his face, the tears he's been fighting for days finally becoming too heavy for his eyes to hold and falling down his cheeks."Cas, god it hurts so much. I'm so scared." He's about to go on but Cas does something that stops him.

He leans forward and presses his lips to the mark, kissing it gently. It quiets Dean, calms him. When Cas lifts his lips he then moves a hand to Dean's eyes and wipes away his tears.

"It'll be okay, Dean. We will get through this together." Dean looks down at their connected hands and feels a pang of hope.

"Right." He says, his voice trying to return to its normal strength. "Together."