A/N: Filling an anonymous request on Tumblr, asking for a what-if where Cas is still in Purgatory when Sam goes through from the rescue-Bobby-from-Hell mission. Here you go, anon!

Setting: Alternate season 8, Taxi Driver specifically.

Summary: Dean came back from Purgatory. Cas did not. If the Winchesters had even suspected he was still alive, they would have crossed every line to get him back, but Cas was gone. Wasn't he?

Coming Home

This can't be real.

Shifter, Sam automatically thinks, though he already knows this is the genuine article. Beyond all doubt, beyond all reason, deep down Sam knows.

Cas stares back at him, eyes registering horror.

"No!" the angel exclaims before Sam can muster any words. "You shouldn't be here!"

"Sam?" Bobby asks from behind the hunter. "I thought you said you boys lost Cas?"

"We did," Sam chokes out, voice like nails and gravel. "Cas… is it really you? But Dean said…"

He doesn't wait for the angel's confirmation to close the distance between them. He doesn't wait to do the myriad of tests he should do first, because really isn't it more likely this is just a shifter? After all… Purgatory is full of monsters.

But Sam doesn't care about logic or proof. All the proof he needs is standing in front of him, in ratty white scrubs and a torn overcoat. His proof is right there, with dark circles underlining half-empty eyes.

Sam clings to that proof as he clings to Cas. "Dean said you were dead," he hoarsely whispers as Cas's arms come up hesitantly to return the hug. "I thought we'd lost you… Cas, have you been here all this time?"

His heart breaks. Not only at the idea of Cas being trapped here on his own, but also because Dean is going to shatter to learn he mistakenly left the angel behind.

"I suppose so," Cas replies, not pulling away but not engaging much either.

"But… Dean got back six months ago." Six months of living with a hole where Cas's presence used to be. Six months of Dean's guilt-ridden anger exploding at every turn. Sam becomes aware of Bobby still behind them, shifting slightly from foot to foot. It hits him then that if he hadn't come through here to rescue Bobby's soul from Hell, they might have never found Cas, and suddenly Sam can't breathe.

"Dean thought I was dead?" Cas asks.

Sam finally pulls away, rubbing a hand across his eyes. "Y-yeah," he stammers. "Right as you two and the vampire were about to get through the portal."

"Hmm. I don't know why he remembers it like that."

Sam's heart stops once again. He knows his brother would not—could not—have left Cas intentionally. But then why had he remembered wrong?

"What happened?" he practically pleads.

Cas looks away. "I didn't leave with them. You and Bobby have to go. How did you even get here? You aren't dead, are you?"

"I am," Bobby supplies. "He's not. And Cas is right, it's time to get."

Sam nods. They can catch up later, after he brings Cas back to Dean. "Alright. Come on, there's a reaper waiting to-"

"Sam, I'm not going."

Castiel's eyes are full of pain. It burrows into Sam's soul.

"…What?"

He sighs. "I can't go back. All the wrong I did… I have to stay here. To atone."

Sam is not having this discussion. In his heart, he's feared this from the moment he saw Cas still alive. He grabs his friend's arm.

"No. You don't. Cas, we've all screwed up. We've all broken things. This isn't atoning. Getting back out there, fighting the good fight, that's how we make things better. We need you to come back. We need you. I know what you did, Cas. And I'm telling you, you don't deserve this."

Cas closes his eyes. "How can you even bear to be near me?"

"Because you're my friend. Nothing else matters."

Silence draws on, the grey forest eerily still as the three stand suspended in time. Sam tightens his grip, terrified the angel might fly away if he doesn't hold on for dear life.

"Please," he begs softly. "Please come back. Don't make me tell Dean I failed to bring you home. We can work this out, just please, please give me a chance."

It looks like Cas is wavering. "I'm hopeless," he tries.

"Nothing is hopeless. Not even me. Not even you."

"I broke your wall."

"I healed. Don't break me again now."

Finally, Cas meets his eyes, more sad than stubborn, more lost than found. But Sam will do anything it takes to change that.

"Okay?" he asks.

Cas pauses. Then he nods.

It's time to go home.