Dean would never forgive himself.
He was stupid and reckless, and when it came down to it, he couldn't pull the trigger.
The Shtriga almost killed Sam, and if it wasn't for his dad coming back at just the right time, it would have.
Dean had been terrified. He had never faced a monster on his own before. He had been on a few simple hunts with his dad, but they had been that: simple. There was a reason his dad went to hunt the Shtriga down solo. And when Dean saw the creature, and what it was doing to Sam... well, he froze.
"I can't believe you could be so stupid, Dean! God damn! That thing almost killed your brother, and you couldn't even pull the fucking trigger?" His dad was yelling, but Dean was sure he'd be screaming at the top of his lungs if Sam wasn't asleep in the other room. After he was sure Sam was okay, he got rid of the body and came right back to deal with Dean.
"I-I'm sorry..." Dean truly was. He didn't need his dad to tell him what a horrible brother he was for letting that happen. He should've known better. He should have never left Sam alone in the room. He should've known better. He'd been watching out for that kid for five years now. He should've known better.
"What did you say?" John put his hand to his ear as if he didn't hear Dean's tiny voice.
"I'm sorry, I-" He felt the back of John's hand collide with his cheek, and then he felt blood on face.
"Sorry isn't good enough, Dean! Not if you go and get your brother killed!" John grabbed Dean's arm and yanked him forward, until he was close enough that Dean could smell the alcohol on his breath. "You won't let this happen again, right Dean?"
Dean shook his head. "No, sir. Of course not."
John let go of his arm. "Good. Now get out of here. Go in the room with your brother. Try not to get him killed, okay?"
Dean hurried into the bedroom, closing the door behind him. Before he could bring himself to even look at Sam, he turned to the mirror and tried to get his cheek to stop bleeding. There was a small cut right where his cheek met his mouth. It hurt a lot, but there was blood in the way and he couldn't tell how bad it was.
Dean turned at Sam's small, tired voice. He was sitting up in the bed, still covered in blankets. His hair was a mess, and he looked exhausted, but otherwise he looked perfectly fine. "Hey, Sammy. What are you doing, awake?"
"I heard you come in. What's wrong with your mouth?"
Dean pressed his fingers over the cut, which had stopped bleeding, but there was still some dried blood left. "Nothing, I just... tripped, that's all. Sorry for waking you up, kiddo. Go back to bed."
Sam stared at him for awhile, but eventually agreed. "Okay..." He laid back down into his pile of blankets.
Dean turned back to the mirror, wiping blood off his chin. There was a red spot on his cheek, but that would go away soon. He climbed into bed next to Sam, who was still mostly awake. "Hey, Sammy," Dean brushed back some of his hair, which was getting longer everyday. Sam scrunched up his nose, like always. "Can I ask you a question...?"
Sam nodded sleepily. "Do you remember what happened, earlier? Before dad got back?"
Sam thought for a moment and shook his head. "I remember feeling really tired, and it kinda hurt but then it stopped."
Dean nodded. He quickly thanked God for small miracles. "Okay, Sammy. You can go to sleep now."
"Wait, wait. Dean?"
"Can we play the imagining game?"
A small smile grew on Dean's face. "I thought you were too big for the imagining game. Remember, you told me that you were almost five years old, and five year-old's don't play that game." It seemed like everyday Sam was outgrowing something. Sometimes it was a shirt or a new pair of pants, and sometimes it was a game that he officially could not play anymore. He was growing up so fast, and Dean loved every minute of it.
Sam stared at Dean, and made the straight face that he always made when he was trying to convince Dean of something. It was very business-like and professional, and Dean thought it was adorable. "Yeah, Dean, five year-old's don't play that game, but I'm almost five, and almost five year-old's can play."
Dean grinned. "Alright, fine. But you have to close your eyes."
While he played the imagining game with Sam, he couldn't help but think of the Shtriga. He had really messed up today, big time. If his dad had gotten there any later... well, Dean didn't even want to think about that. But it was nice to know that no matter how bad he messed up, no matter how pissed his dad was at him, Sammy would still want to play with him. Sammy still needed him, and that was all that mattered.