Summary: Season Nine – Sassy Abaddon / Vulnerable Sam / Big Brother Dean – Dean felt dread crawl up his spine, suddenly knowing what Abaddon had realized...that Sam was unprotected from possession. In the next instant, Abaddon's head flung back, black smoke erupting from her mouth and swirling in the air before streamlining straight toward Dean's little brother.

Disclaimer: Not mine.

Warnings: Spoilers for season nine, plus usual language.

A/N: A oneshot inspired by the E/O Challenge word-of-the-week (key).

I always tell the truth even when I lie. ~ Scarface

"Hello, boys..." Abaddon greeted in that smooth, sultry way of hers.

In that way that was vaguely sexy.

In that way that reminded Dean that red hair and black leather was one of his favorite color combinations.

In that way that would've been enticing as hell...if she wasn't a demon from hell.

"Fancy meeting you here," Abaddon quipped, her glossy red lips quirked in amusement as her gaze flickered between the brothers before settling on Sam.

Standing in the middle of the warehouse, Sam exchanged glances with Dean while Abaddon nodded her approval; her smile widening as if she had just discovered the key to a previously locked door.

Dean felt dread crawl up his spine, suddenly knowing what the demon had realized – that Sam was unprotected from possession.

The big brother glared at her in warning.

Abaddon winked at Dean – completely unfazed – and then refocused on Sam. "It's like looking at a naked Winchester," she remarked, comparing the missing tattoo to missing clothing.

She paused and nodded again.

"Mama likes," she purred and smiled at Sam suggestively. "Oh, the fun we're gonna have together, lover..."

Sam shifted – uncertainty and fear in that one movement – and glanced at Dean as Dean stepped in front of him, pushing Sam back.

"No," Dean growled, piercing Abaddon with another heated glare. "If you wanna fuck with somebody, fuck with me. But you leave Sam alone. You leave him out of this."

The demon laughed.

"Oh, Dean. Haven't you learned by now that as long as you're in, Sam is never out? Besides, I wanna fuck with both of you," she admitted and smiled at the thought as if she knew the best way to fuck with Dean was to fuck with Sam.

Dean's glare intensified, feeling the burn of rage surge through him.

Abaddon watched him, shaking her head like a disapproving schoolmarm. "Temper, temper..." she scolded and wagged her finger at Dean. "Haven't you also learned by now that nothing good comes from all this pent up emotion?"

Dean said nothing but continued to quietly fume; his body humming as adrenaline flooded his system in preparation to fight.

Because no matter how shitty Sam had acted lately...or how strained their relationship had become over the past few weeks...Dean would always fight for Sam, would always protect his little brother.

Abaddon sighed as if Dean was overreacting...and she was bored.

"Relax, big brother," she further soothed even as her gaze slid back to Sam, staring at him as if she had big plans for Dean's kid. "I have a lot of experience behind the wheel, and I'll be gentle with your little Sammy," she promised like a new babysitter trying to comfort a nervous parent...or a test driver trying to sweet talk the car dealer. "I just wanna take him out for a spin. Just to see what all the fuss is about..."

Like the entire supernatural world was abuzz with what it was like to ride Sam Winchester.

Sam swallowed at the thought, feeling vaguely nauseous.

Dean felt a fresh stab of guilt through his chest for his role in Sam's most recent possession...and for his role in removing his brother's protective tattoo.

They should've gotten it replaced weeks ago.

They had talked about it several times.

But they hadn't done it.

And now...

"Angels and demons and even Big Daddy himself all seem to agree that your little brother is one hell of a thrill," Abaddon continued, glancing at Dean and then back to Sam. "And what can I say? I'm a thrill seeker."

Sam stared at her with wide eyes, speechless at the idea of what could happen; at the potential reality of once again being possessed and having no control over his own body.

"You'll be fucking dead if you touch him," Dean told the demon, making a promise of his own; his calm, steady voice somehow lending more power to his words as he continued to stand in front of Sam.

Abaddon shivered dramatically and licked her lips. "Mmm..." she moaned as if she was aroused. "I love it when you talk dirty, baby. When you're all hot and bothered and lethal..." She smiled. "Really gets my engine going."

Abaddon paused, clearly enjoying this.

"But unless you have the First Blade, I think we both know you're all talk and no action," she taunted. "Because the Mark of Cain is only half of what you need to even begin to be a threat to me."

She smiled at Dean, her gaze lingering on the welted mark branded into Dean's forearm before he tugged down his sleeve to more fully cover it.

"Aw, you're so cute when you're shy," Abaddon pretended to flirt and winked at him.

Dean maintained his glare.

Abaddon stared at him. "I can see why Cain gave you his Mark," she commented, becoming briefly nostalgic. "You're like him in so many ways...except it seems you have the desire but inadequate equipment. Can't quite get it up, if you catch my drift..."

She laughed as Dean scowled at the implication that he was unworthy of the Mark, was inept as a hunter and impotent as a killer.

"Oh, don't worry, sweetheart," Abaddon reassured like a placating girlfriend. "It happens to a lot of guys..."

She hummed another laugh and then sighed, once again sounding and looking bored.

"Well, this has been fun...but I'm a busy girl," Abaddon reminded them, glancing around the warehouse. "Hell's not gonna run itself. And I've got places to go and lives to destroy and...people to possess."

In the next instant, Abaddon's head flung back, black smoke erupting from her mouth and swirling in the air before streamlining straight toward Sam.

Dean watched, his heart hammering in his chest as he glanced over his shoulder, double-checking Sam's position and hoping like hell their plan worked.

Sam's eyes widened as he braced himself, instinctively reaching for Dean.

Dean reached back, holding his brother steady as they waited...and also holding his breath, because this had to work.

This last-minute plan had to repel Abaddon and protect Sam.

Because if it didn't...they were so fucking screwed.

Dean swallowed, terrified by the possibility of the demon possessing his brother; of Sam once again being lost to him.

Sam was terrified as well.

Dean could hear his brother breathing fast and shallow behind him, and he tightened his grip on Sam's arm, offering support and comfort...and then smiling when the black smoke abruptly stopped; briefly clumping as if it had struck an invisible wall and then dispersing in scattered confusion.

The black smoke churned in the air – Abaddon clearly pissed by the unexpected turn of events – and then rerouted itself, rushing back to its abandoned meat suit lying in a motionless heap on the warehouse floor.

Sam still gripped his brother's sleeve as Dean squeezed Sam's arm in silent victory and continued to stand in front of his little brother.

The black smoke filled its meat suit, reanimating Abaddon's body.

"A Devil's Trap?" she growled as soon as she was back inside and had regained her feet, her eyes flashing black as further testament to how angry she was at being tricked. "Seriously?"

Dean shrugged. "Worked, didn't it?" he quipped about the Devil's Trap he had drawn earlier on the warehouse floor with black light paint while he and Sam had waited for Abaddon's arrival.

The classic demon ward having proved effective in blocking Abaddon from reaching Sam as he stood in the center of the invisible trap.

Abaddon's eyes returned to normal as she glared at Dean. "You think you're smart, don't you?"

Dean shrugged again. "I get by."

Abaddon snorted and shook her head. "Not for long," she replied. "If I want Sam, then I'll take him eventually."

"And here I thought you wanted me..." Dean pointed out, changing the subject from his little brother and reminding the demon of their encounter back at that contaminated city block where she had threatened to rip off Dean's tattoo in order to possess him.

Abaddon twitched a smile, knowing Dean was baiting her. "I do want you," she told him. "I would take great pleasure in destroying you from within...especially now after this little stunt."

She gestured at Sam still safely tucked behind his brother inside the Devil's Trap.

"But I can't possess you," the demon continued, both pissed and disappointed at being denied what she wanted. "Not only do you still have your precious tattoo, but now you also bear the Mark of Cain. That makes you doubly protected and an even bigger pain in my ass."

Dean glanced down at his arm where the Mark was still hidden beneath his sleeve, having no idea it also granted him protection from demon possession.

But that was no surprise.

There was still so much they needed to learn about this Mark that Dean had impulsively accepted over a month ago.

"But unlike you..." Abaddon countered, once again returning her attention to Dean's little brother. "Sammy is stripped bare. The most adorable sitting duck I've ever seen..."

Dean narrowed his eyes at the threat. "We'll see about that," he challenged her, planning to take Sam to the nearest tattoo parlor as soon as they left the warehouse.

"Yes, we will," Abaddon agreed and paused, seeming to consider whether or not she wanted to say what was on her tongue.

Dean blinked expectantly.

Abaddon smiled. "I know Crowley is searching for the First Blade," she revealed and then shrugged at Dean's startled expression. "There are no secrets from the Queen," she reminded, her smile lingering as she enjoyed one of the many perks of her power and reign.

Dean said nothing but his stance remained protective as he continued to stand in front of Sam...and his expression became cautious as he waited to see where this conversation would lead.

Sam also kept quiet, watching and listening.

Abaddon watched them in return like a spider watches a fly.

"If Crowley finds the First Blade...even though it's contained in the largest body of salt water on earth..." she remarked, her tone pointing out that demons and salt didn't usually mix well. "And if he actually delivers it to you..." she further hypothesized, her tone changing to reflect her doubt about that as well. "...then I suggest you begin making your peace with killing your brother, Dean."

Dean frowned at the statement, his heart momentarily stuttering to a stop. "What?"

"You heard me," Abaddon replied, her gaze flickering between the brothers. "Cain warned you that the Mark you now bear would come with a great cost and burden. And what greater cost is there than the life of your darling little Sammy? What greater burden to live with than knowing you were responsible? Knowing that he died by your hand...just like Cain and Abel."

Dean snorted and shook his head. "Right. And why should I believe a lying bitch like you?"

"Because you know I'm not lying," Abaddon smoothly returned. "The chasm between you and Sam has been growing wider by the day. The resentment, the's all part of the plan."

Sam shifted uncomfortably, glancing at Dean as neither brother could deny the recent strain in their relationship.

"Cain loved Abel," Abaddon continued. "Loved him and protected him right up until the day he didn't. And then..."

Her voice trailed off as she slid her finger from ear to ear, miming her throat being slit and indicating Abel's death.

"So tragic," Abaddon tsked as if she actually gave a shit. "Cain was never the same and – "

" – shut up," Dean growled, annoyed by the demon's rambling. "What Cain did has nothing to do with me. He made his own choice about his brother."

"He did," Abaddon agreed. "And what's your track record for making choices about your brother?" she asked and then smiled knowingly at Dean's expression. "That's what I thought."

Dean glared, refusing to allow the demon to get under his skin. "Fuck you," he spat, wishing he could kill the bitch now for spreading lies about him and his brother.

Because no fucking way would Dean ever kill Sam, no matter how bad things got between them.

Abaddon laughed. "Believe what you want to believe," she told Dean. "You usually do. But I've read ahead. And spoiler alert: this doesn't turn out like you think. Because I will have your brother...and you will kill him. Maybe when you kill him, you'll kill me as well. Maybe you won't. But that's how your story ends - with Sam's blood on your hands."

Dean clenched his jaw at the prediction, his heart pounding as his glare burned hot.

Abaddon laughed again and then glanced at the warehouse door as one of her demon minions suddenly appeared, tilting his head toward the outside as if something urgent had just developed that needed her attention.

Abaddon sighed. "A Queen's work is never done," she quipped and then smiled at the brothers. "See you 'round, boys..." she called over her shoulder, turning and walking toward the warehouse exit. "And Sammy..." she added, pausing in the doorway as she stared at Sam still standing inside the Devil's Trap. "I'd watch my six if I were you. Never know when big brother will stop playing nice..."

And with that, she was gone.

Silence settled, echoing in the vastness of the warehouse.

Sam shifted uneasily as Dean turned to face him.

Dean arched an eyebrow. "Don't look at me like that," he admonished his brother. "You know I'd never hurt you."

"I know," Sam assured, his gaze landing on Dean's arm. "Unless something else was controlling you...was controlling us."

Dean pushed up his sleeve, revealing the Mark of Cain.

Sam continued to stare at it.

Both brothers knowing that demons lied...except when they told the truth.