It started when Sam first met Cas, and in that instant, Sam knew exactly where he was headed. Not that he hadn't felt it before, but this was just so…wrong.
"The boy with the demon blood," Cas had said.
Sam was dirty, impure, in more ways than one, and he knew it. Though the vessel was a man named Jimmy, Cas's voice was deeper. It struck a feeling into Sam that he hadn't felt in a long time.
Then, the dreams. Fantasies. Castiel would show up in his room, talking in his deep sultry voice, pushing Sam onto his bed, forcing their lips together. Then, he'd wake up. He'd always wake up before anything happened. It'd made him feel worse than the demon blood.
Dammit Sam, he told himself, He's an angel, what's WRONG with you? He stayed with Ruby, a demon, but at least female. Always with Ruby. After Dean died, she helped him, and he loved her. Loved a demon. She betrayed him.
Cas tried to help them, which only made Sam love him more. Cas gave up, Sam became the vessel for Lucifer. Then, Sam became powerless.
"I know about Cas, Sammy," Luci said, "I'm in your head. You won't have him."
Sam was powerless to watch as Cas exploded.
"No!" Sam screamed from within, "Cas!"
Lucifer laughed.
"I told you," He told Sam.
He killed Bobby as well, nearly killed Dean.
Cas returned, Jimmy was dead, and Sam was in hell. Worse, the cage with Lucifer. He felt guilty, as if he'd personally failed Sam. After wallowing in self-pity for about a week or so, he made the journey to pull Sam out of hell. It would be hard, harder than getting Dean out, as the cage is further down.
The cage itself was easy to find. In a place of pure darkness and silence, it stood out. The fire, the screaming, from Adam and Sam both. Cas hated the sound, humans being tortured, ANYTHING being tortured really. He couldn't carry the both of them out, so he had a choice to make. Reluctantly, he chose Sam.
"Hello Castiel," Lucifer said as Cas entered the cage.
Cas froze with fear, Lucifer was truly horrifying in person. Sam lay at the ground of Luci's feet, skin charred, disoriented.
"Brother," Michael was concerned, "What are you doing here?"
"I came to save Sam," Cas said, weary of Luci.
Michael picked up Sam and gently handed him to Cas. He'd been the one attempting to protect Sam and Adam from Lucifer's wrath.
"Hmm," Sam moaned, unable to move.
"Shh," Cas said, "It's going to be okay Sammy."
"…not real…"
Luci lunged at Cas, but Michael held him back.
"Go, Castiel," Michael demanded, "Hurry."
Cas grabbed Sam and made his way out of the cage.
"You'll pay for this, Castiel!" Luci yelled, "I will tear you apart! I will kill everyone you love!"
Cas panicked and ran out with Sam. He didn't hear Michael yelling that Sam's tattered soul had been separated from his physical body over the sound of Luci describing everything he'd do to Cas in explicit detail.
Sam woke up in the field, feeling strange. Handprints were on both sides of his hips. Cas left him, decided not to tell Sam what happened. After all, he didn't really have a reason for pulling Sam out of hell. Well, maybe one.
It took Sam nearly a year to find Dean. All the things Sam did without a soul. Very little of which he remembered after he got it back. When Cas felt for Sam's soul, he was guilt ridden again. He had left Sam's soul behind, due to his own fear and negligence.
"Did you leave my soul behind…on purpose?" Sam asked.
Cas was hurt by that. To imply that Cas would intentionally leave Sam's soul behind, a soul which felt like it had been "skinned alive", was to imply that Cas wanted Sam to burn, which is simply not true.
He broke Sam's wall, swallowed the Leviathans, killed so many angels. In his own opinion, he didn't deserve to live.
Sam went insane. Cas returned, remembered what he'd done and took on Sam's insanity. He had to, he deserved it. He loved Sam. He loved Dean as well, but not to such a degree. In fact, he'd never loved anyone to this degree. He could never forgive himself for causing Sam so much pain.
Sam didn't want to abandon Cas in the hospital, but Dean convinced him to. He never got Cas out of his head. When Cas woke up, friendly and strange, he still remembered Sam, kept him in his dreams.
In purgatory, Cas stayed behind on purpose. He deserved to be in there. His punishment for betraying everyone: the angels, the Winchesters, Bobby.
He got out, though under control of Naomi. He went to Sam.
"Cas?" Sam asked, surprised as to why the angel had shown up at Sam's bedside.
Cas sat at the foot of Sam's bed.
"I'm sorry," Cas said.
"For what?" Sam was confused.
"Making you soulless," Cas said, "Breaking your wall, killing the angels, releasing the Leviathans…all because of me."
Sam put his arm around Cas.
"Cas, it's fine," He said.
Cas rested his head in his hands.
"No," He said, "I should be d…"
Sam leaned Cas toward him, Cas putting his head on Sam's shoulder.
"Don't say it, Cas," He said, "We need you. I love you."
Sam tilted Cas's head. Cas furrowed his eyebrows.
"Sam?"
Sam pressed his lips against Cas's
"I love you," He said, "I always have."
"I love you, too."
Cas ran his fingers through Sam's hair and they kissed again.
"Shit!" Sam exclaimed.
"What is it?"
"Dean's back."
Dean had returned from the store. Cas fluttered away.
