Faith's eyes went wide with fury and Sam looked between them nervously. "Dean," he hissed. "I think she'll kill you!"
"You're so full of crap it's almost cute," he continued, completely ignoring his brother. "You know something."
"What the hell could I know?" she demanded.
"Something," he said a bit childishly.
"I don't know anything." She crossed her arms and glared at Dean who glared right back. "Okay then. Say I am hiding something. What do you suppose my motives are?"
"Spite," was the immediate reply.
"Really?" she demanded. "Spite. You don't think my motives might be a little bit more noble? Or that I actually don't know anything?"
He smirked a bit. "You might hate me, but I know you… Annie. And you're lying. Badly too."
"Yeah, I know you too, Dean," she said with a taunting smirk. "What're you gonna do to make me tell the truth? Smack me around a little?"
"I'm not playing here," he warned her.
"You think I am?" she demanded darkly. "I've known you long enough, Sam's part of my family too. Don't you even pretend like I don't care!"
He got right in her face and she didn't even blink. "Who's pretending?" he demanded. "I'll flat out say it- if you cared, you wouldn't leave this alone. You'd do something."
"Maybe there's nothing to do," she shot at him, unflinching as they stood toe-to-toe. "Maybe Sam's a lost cause."
Dean's eyes narrowed and he snarled, "You of all people…"
Sam watched in silence as they stared each other down, wanting to get between them, but afraid of what they'd to to him if he tried. Either one of them, he would bet on winning a fight against anything that challenged them, but against each other… Sam wasn't sure he wanted to see the bloody mess that would turn into.
"Get out," Faith ordered calmly, finally breaking the silence. Dean didn't so much as blink. She said a bit more forcefully, "Sam, I said get out." Sam looked between Faith and Dean in surprise. She added, "And don't try to listen at the door."
"Sam, go," Dean snapped as they very cautiously stepped back from each other.
"Dean-" he started to protest, but stopped when Dean broke eye contact with Faith to glare at him. He nodded once then closed the door behind him as he left.