Dean was getting worried about Sam. He spent most of his nights outside, staring at the sky or reading in the library. He looked like he hadn't slept in weeks and he barely ate. Dean suspected that it had to do with Kevin's death, and his suspicion was confirmed when he went searching through Sam's room.

In the top drawer of his desk were letters, about 30 of them, all addressed to Kevin. All of them basically said the same thing: I'm sorry, please don't hate me, I miss you. Dean felt a pang of guilt in his chest. He knew that his little brother blamed himself, it didn't matter how many times he was told the opposite. Dean kept looking through the letters until he found one that was different than the others. It was dated the night before and it read:

"Dear Kevin,

There are no words left to describe how truly sorry I am for what happened to you, what I did to you. I told you from the beginning: you deserved better than me.

We always talked about getting out of the life and settling down, just me and you. I can't believe I was stupid enough to think it could actually happen. I wish it could. I wish it had been me instead so you could live that dream one day. I don't want it without you.

I miss you so much. Being without you is painful. I can't live with myself knowing that it's my fault you're gone. So I'm coming to join you. I'll see you soon.

-Sam"

Dean had been worried before, but he was panicking now. Sam had gone for a walk about an hour ago, who knows what could have happened by now. He ran outside, hoping it wasn't too late, hoping his brother was okay.

Sam had two places he liked to go when he went for walks: the creek and the clearing he and Kevin used to go to. The clearing was closer so Dean ran there, stumbling over branches and roots in the darkness. He hadn't thought to bring a flashlight, but thankfully he had his cell phone. He turned on the torch when he got there, scanning the grass and surrounding trees for any sign of Sam.

There was a dark figure at the other side of the clearing, still and crumpled. Dean walked over, muttering under his breath, praying it wasn't Sam. He didn't need to get very close to realize that it was. "Sam?" Dean yelled. "Sammy?" He didn't move.

He knelt down on the ground beside his brother, tears stinging his eyes. Dean grabbed Sam's shoulder, flipping him onto his back. "D...D...Dean," Sam stammered. His cheeks were wet with tears and he was clutching something against his chest. "I killed Kevin. It's my fault he's gone," he sobbed.

"No, Sam, it isn't. It's my fault, not yours," Dean replied, a no-nonsense tone in his voice.

"Yes, it is," Sam insisted. "I see it happen every time I close my eyes. I see myself killing him. It's my fault he's dead. It should have been me..."

"Sammy, it was Gadreel. I was the one who tricked you into letting him in. It's my fault," Dean argued. Sam just shook his head, too tired to fight. He knew that neither of them would change their minds.

"I can't do this anymore," Sam whispered, his voice hoarse. "I can't keep going. I'm so tired..."

"You have to stay with me. We'll find a way to make it better, we'll figure something out. But I can't do it without you," Dean told his brother earnestly. "I need you to keep going." He took Sam's arm and dragged him to his feet. "We can do this." He led Sam back to the bunker, guilt coursing through his body.

"Go to bed," Dean commanded as gently as he could, bringing Sam to his room and making sure he'd stay there. He couldn't bear the thought of waking up without his brother. He didn't want to. From the day Sam was born, Dean knew he'd protect him.

He left Sam's door open a crack, checking in on him periodically. Dean couldn't sleep knowing what Sam had been considering. He couldn't risk falling asleep and not being able to save Sam from himself. He'd be okay in the morning. Sam was strong, he was a fighter. He'd keep going. He needed to. Dean needed him to.