What if Lucifer told Dean why Sam said yes?

"I'm not going to let you," Past Dean said to Future Dean.

Future Dean knocked out Past Dean and returned to the group.

"What was that all about?" Cas asked.

"He doesn't understand. He's not from now. He was having second thoughts about killing Sam," he lied to cover up the fact that he was using these guys as a diversion.

"Who's Sam?" Reesa asked.

"Never mind. No time. Go," Dean ordered.

They went. Because they had been following Dean's orders for four years and he hadn't steered them wrong yet.

Dean then ran around to the other side of the building

"Dean, I heard you were here," Lucifer said.

Dean lifted the Colt and shot Lucifer. Lucifer went down. "I can't believe it's finally over," Dean said to himself.

"It's not," Lucifer said and stood back up. "Don't feel bad. There are only five things that gun can't kill and I happen to be one of them."

"I assume you're going to kill me now," Dean said, beyond caring at this point. What he had been doing the last few years wasn't living, and now he didn't even have a clue as to how to kill Lucifer, so he was sure he'd be better off dead.

"First, let me tell you a little story."

"Great, a monologue before I die."

Lucifer smiled. "Oh, Dean. So sarcastic all the time. You might be interested in this story, though."

"I doubt that."

"I'm going to tell you the story of how Sammy said yes."

That did peak Dean's interest. He could never understand how that had happened. "How do I know you'll be telling the truth?"

"I have no reason to lie if I'm going to kill you and Sam wants you to know."

No, I don't, Sam screamed from inside Lucifer. Just let him go.

Lucifer smiled. "So, three years ago, I unleashed the Croatoan pandemic on the world. You know that much. Your brother is immune. You remember that from the last time you encountered the disease, right?"

"I remember," Dean said, remembering how it had freaked him out. He was glad he didn't know half of what he knew now, back then.

"So, Sam decided to go to Detroit, where I started the disease to see what he could do. You remember he called you for help and you told him to deal with it. You were busy."

Dean remembered that also. That had been the first time Sam had called him in two years and Dean was in a groove, hunting with Cas, getting research from Bobby. He had never forgiven Sam for drinking the demon blood and choosing Ruby over him. He wished now that he had.

"Anyway," the devil continued, reveling in Dean's discomfort, "I had a couple of demons go out and capture Sam and bring him back to me. I forced a whole bunch of demon blood down his throat. Then I manipulated his hallucinations. It was all you, Dean. You telling him what a disappointment he was, how much you hated him, how you wished he had never been born. Then I came to him and told him he might as well say yes, because he had nothing. Oh, he resisted a few days longer, but he was beaten. The only thing that ever gave him strength was you and your encouragement. He would have killed himself after Jessica died if it wasn't for you. You could have stopped him from saying yes, you and only you. I just thought you should know this was all your fault."

No, Dean. It was my fault. I was weak. Don't listen to him.

With that Lucifer threw Dean down to the ground and placed his foot on his neck. "We're going to break his neck now, Sammy. Pay him back for everything he ever did to you."

NO!

Dean looked where he was forced to look and saw his past self running up. He wanted to yell to him to go back to Sam when he got back to '09. Wanted to tell him to forgive Sam. But, the devil broke his neck and he knew no more.

"Oh, hello, Dean," the devil said. This Dean was from the past he could tell. He wouldn't be telling this Dean that tale. He wanted him to go back, ignorant of what happened with Sam, so that it could happen all over again.

DEAN! Sam could tell the difference. This Dean was not the Dean the devil had just killed. This was his Dean. The one that might still care about him. He scratched and scrabbled trying to get control, but he had been submerged too long.

Shut up, the devil said to him and he felt himself falling asleep.

Lucifer turned his attention to Dean. To tell him that no matter what he did, they would always end up back here.

The End