Sam was sixteen the first time he encountered a shapeshifter.

The thing had jumped Dean coming home from a bar in the French Quarter one night and left him unconscious, cuffed and chained to a drain pipe in an abandoned warehouse. For four days and nights, the creature stayed in the motel room with Dean's little brother. It drove the boy to school in the mornings and picked him up in the afternoon. Sometimes it dropped him at the library or took him out for pizza. The thing slept in the bed across the room from Dean's brother at night, and it even took the boy on a hunt for werewolves in the next town over because Dean's dad called and yelled and made it afraid not to go.

At the end of the fourth day, though, the thing came to the realization that Dean's little brother was a pain in the ass. It realized that it had, in fact, jumped into the body of someone who was essentially the parent of a moody teenage boy and that the work involved was more than the thing desired. But it knew that simply leaving in Dean's car was out of the question. It had gotten to know the boy well enough in that short time to understand that it would be followed wherever it went.

That's when it made the decision to kill the boy instead.

The creature liked the body it had hijacked. The body was strong and able. It was a good and efficient fighter. It was also pretty, and the creature liked that especially. It had never been pretty before. It soon learned that pretty meant power, and that it could talk people into doing just about anything by amping up the charm and flashing the pretty man's smile.

The body was convenient, and the creature was loathe to give it up.

So on the evening of the fourth night, the creature waited until Dean's brother was asleep, and then it slipped the sharp, silver knife out from under the man's pillow. It crept silently to the other side of the room and crawled atop the boy, raising the knife high. The boy woke up then, but he didn't struggle. His eyes widened when he saw the creature that looked like his brother leaning over him with a knife, but he stayed stock-still anyway.

He trusted the creature not to hurt him. The thing could feel it.

But then Dean exploded into the room at that exact second, saw the thing on his brother's bed, and tackled it to the floor - all before the knife had time to descend.

And when Dean stabbed it in the chest with the silver knife, the thing died instantly, without even having time to regret not leaving in Dean's car after all.

It was in the moment after that all hell broke loose.

"Sammy!" Dean crawled into his brother's bed and shook him gently. "Sam! Talk to me! You alright, man? That bastard do anything?"

But Sam was in shock. He'd awoken to Dean leaning over him, knife raised high, and then suddenly Dean wasn't Dean anymore, and there was something dead on the floor that looked an awful lot like him.

"Dean?" He finally managed, staring into his brother's eyes.

"Yeah, it's me. It's REALLY me, this time. That fugly thing jumped me in the street and chained me to a freaking pipe." Dean reassured himself with a gentle hand on the back of his brother's neck, so relieved to see him alive and well that he nearly couldn't speak. "What about you? You okay? That bastard was about two seconds from driving my knife into your chest!"

Sam's hand went to his chest then, just to see if there was anything like a silver knife protruding from it. He looked up in confusion. "Yeah. No. I mean, yeah, Dean. I'm okay. I didn't know it wasn't you."

Dean stared into his brother's eyes. "Really Sam? The thing was with you for four days? You had no idea?"

Sam shook his head sadly. "No. I mean, there were some things that seemed … off. But not that much really."

"Off? What do you mean off?"

Sam tried to think. "Well, I mean, you were eating your hamburgers really rare. And you weren't drinking beer at all, but that's about it, I guess."

Dean stared. "And that didn't tip you off? What the hell, Sam?"

Sam just shrugged. "I guess not."

"Damn. You were two seconds from dead. You got to be more observant, dude."

Sam shrugged again. "It looked just like you, Dean. It acted like you. It had your memories. I mean, it knew to take me to school and pick me up again. Even Dad didn't know."

Dean shook his head, "Dad did know, Sam. He's the reason I got free. He came looking for me after you and that … that thing … joined him on the hunt. Dad knew it the moment he saw the thing."

Then it was Sam's turn to stare. His face turned pale. "He knew, and he didn't say anything?"

Dean realized then what Dad had done, and he tried to backpedal. "Well, I guess he thought you'd been okay this long …" then his voice trailed off, realizing that his father had endangered his brother's life by not getting him away from the shapeshifter right away."He didn't say anything at all?" he asked incredulously.

Sam shook his head, "You mean he thought I deserved whatever I got." Sam said softly. "Dad knew I was locked in this motel room with a shapeshifter, and he thought since I was too dumb to figure it out on my own, I deserved whatever happened."

Dean stared silently at his brother, rage for his father building. Still, he tried to defuse the situation. "I'm sure it wasn't like that, Sammy." He tried to reassure the boy. "Dad, just … sometimes he … I mean, he doesn't always know how to handle … things right."

"Bullshit!" Sam barked. "You mean he doesn't know how to handle me right. Who does that, Dean?" Sam demanded, his eyes tearing up. "Who lets their son come and go with a damned shapeshifter and never drops a hint?"

"Sam …"

"He came looking for you. He was concerned about you. To hell with me, right?"

Dean sat gazing at his little brother - the only person he really gave a damn about anywhere on the whole fucked-up planet - and felt everything he was feeling - anger, fear, embarrassment.

But mostly, he just felt betrayed. He felt betrayed by his father because his father had information and kept it to himself. And as a result, Sam had nearly died.

His brother was right. Who did something like that?

"Sammy … " Dean started, throat choking up. He was suddenly so angry with John Winchester that he nearly couldn't breathe.

Sam sighed. "It's fine, Dean. I mean, it's not like I'm not used to it, right? Dad has never …" Sam turned his head away then, eyes watering, and swallowed hard.

But Dean just pulled him close in a hug and whispered in his hair, "Sammy, when I came through that door and saw that thing hovering over you with a knife, I thought it was all over. I couldn't have gone on without you, Sam. I mean it."

Sam hugged him back. "I know, Dean. I feel the same way. With Dad … I just. If I didn't have you …"

"It's okay, Sammy." Dean murmured. "I got you now. It's all gonna be fine."

Dean wasn't much prone to nightmares, but he had a whole string of them that night. And in every one, his baby brother died a horrible death while his father stood by and watched indifferently, nodding silently like Sam deserved them all.