(A/N) For my AU prompts series on Tumblr, "strangers on a train" AU

Me: Hey, strangers on a train! This should be fun and easy!

Also me: discards three different ideas over the course of two days

Also also me: spends a week researching various aspects of law enforcement, eventually goes "aw fuckit" and handwaves what's left

"Most people are nervous about flying."

"Hmm? What?" Cisco Ramon looked up.

The woman sitting across from him lifted her eyes from her book. "I said, most people are nervous about flying. Not taking the train."

He studied her. She had big brown eyes and long dark reddish hair twisted into a braid, and she wore a suit and a cool, unapproachable expression. She looked like someone who was going to a meeting in another city about accounts receivable or stocks and bonds or something. She didn't look like a chaos villain.

Still, there was a reason his vibe had tugged him in this direction as he was boarding, and right now it was going pingpingping on his brain stem. "Oh, well, you know. Just about anything can crash horribly these days."

She considered him for a moment without cracking a smile. "Hmm. Interesting way of looking at it." She went back to her book.

Tough crowd.

His foot jittered again, bumping the seat, and she looked up again. He smiled at her. She didn't smile back.

Well, shit, it was reasonable to be nervous when you'd been dreaming about this train derailing for the past week, and now you were on it and only about 44% sure you'd be able to do something about it. To stop the twisted metal and the twisted bodies, the blood and the screaming -

No pressure or anything.

He took a deep breath and pressed his foot into the floor.

He pulled out his notebook and turned it to the most recent page, which was scribbled all over with notes like red upholstery and white ribbon and blue eyes.

He'd added scrawled, terrible sketches of the disjointed images that he hadn't been able to piece together - a coiled snake, a line of metal studs in leather, a rain of some tiny items spitting at his face.

He hadn't needed to write much about what happened every time - screams and crashes and the shriek of tearing metal. It was all burned into his cerebellum.

But directly in the center top of the page he'd put one word - COLD.

The cold had been overwhelming in every dream. It was impossible to tell where it was coming from, but every time it came he woke up shivering, no matter how many blankets he piled on or how far up he turned the heat.

He rubbed his hand over the worn, dark red upholstery of his seat. Well, got that, he thought wryly. He'd taken this train all his life, so the red upholstery had been one of the first things he'd ID'd.

He looked around, checking faces and matching them to what he'd seen in his dreams. That lady there, knitting - he'd seen her with blood pouring down her face. That guy working on his computer, he'd been screaming. That kid with the earbuds in, playing a game on his phone, had been -

Okay, no, he ordered himself. He was going to stop this, or at least be around to help, and - well. It wasn't going to turn out like that, was all.

He hadn't seen the woman in the seat across from him, he realized, and wondered why.

He glanced at her, and found her eyes flicking back down to her book. She'd been looking at his notes, he realized. "Want me to turn it around so you don't have to read upside down?" he asked sweetly.

"I'm fine," she said. After a moment she added, "Looks like a lot of notes you've got there."

"Just some thoughts for work." He nodded at her book. "Interesting reading?"

"For work," she said.

"Mmmm," he said, and doodled a snowflake in the top left corner of the page. "See, cuz I couldn't help but notice, you haven't turned a page in like ten minutes. So either you're a really slow reader or you're actually not reading at all."

She put the book down. "Well, you're pretty observant, aren't you?"

"I do my best."

"I'm sure you do. Well, I'll give you one warning. Stay out of this if you know what's good for you."

His heart beat in his ears. "Oh, I hardly ever know what's good for me."

She opened her mouth, but at that moment, a burly guy got to his feet a couple of rows up. Standing, he revealed the design on the back of his jacket - a twisted snake.

Cisco's eyes narrowed. Had she been trying to distract him? His bosses kept him on the down-low, it was true, but word might have gotten out.

The woman opposite him frowned, then looked over her shoulder, following his gaze. "Friend of yours?" she said.

He met her eyes. "Never seen him before in my life."

He looked back. The snake was moving toward the front of the carriage. To go to the bathroom?

The bathroom was in the other direction. What was to the front of the carriage was the conductor, and the engine.

Cisco found himself on his feet, and found that she'd risen too.

"I told you stay out of this," she said in an undertone, starting down the aisle.

"Like hell," he muttered back.

She huffed and turned back, and he took the opportunity to flick the switch on his gauntlets. They hummed against his palms and the backs of his wrists, no longer just leather motorcycle gloves but something more.

As he looked at the back of her head, a thin ribbon of white slid down her hair, twisting through her braid. His footstep stuttered.

"Sir," she called out. "Sir, where are you going?"

Snake looked over his shoulder and picked up his speed, reaching out to yank at the door. It didn't budge, and he hit it with his palm.

"Sir, you're not permitted in that section - Sir." She spread her fingers at her sides, and thick mist swirled around them. "You need to stop what you're doing right now. I'm with the U.S. Marshals and my powers are active."

As the other people in the carriage gasped and ducked, Cisco caught his breath.

My powers are active.

That phrase was one of the first things you learned at the academy - identifying that you, as a meta, were armed and dangerous simply by existing. FBI, Marshals, ATF, police, it didn't matter, they all had to memorize it, and they all sneered at movies and TV that got it wrong or skipped it.

"Sir, I'm telling you again to stop what you're doing and step away from the door - "

Cisco's eyes flicked over, and he saw the guy who'd been sitting next to Snake, already half-on his feet. A pattern of studs decorated the collar of his leather jacket. He was already pulling his arms back, teeth bared, focused on the marshal.

Cisco swung his hands up and yelled "CCPD, my powers are active!" Square on the heels of his announcement, he threw a small boom, just enough to knock Studs back into his seat.

The marshal's head whipped around for the briefest of instants, and their eyes met. Hers had turned blue.

The next second, she'd whipped back around and slammed something out of her hands. Mist billowed, Snake's jacket frosted over, and ice coated the lock.

The temperature plunged and Cisco thought, Well, there's the cold - but he couldn't focus on her anymore because Studs was out of his seat again, lurching toward Cisco, arms outstretched. Something like a small hail of rocks or bullets burst out from his palms.

"The fuck," Cisco said, and simultaneously ducked and ripped a breach in the air between them, so that whatever Studs had thrown disappeared harmlessly into the nothing. Cisco zipped it up again and threw a bigger boom, knocking the other meta back. "That's attempted assault with deadly powers," he called out. "Stand down, you're in enough trou - shit!" He had to rip the breach open again to swallow the metal shards.

He didn't duck this time, but leapt, zipping the breach as he did, so he landed on Studs, sending them both to the floor between the two rows of seats. The bigger man heaved and wrestled, slamming Cisco against the seats. He winced as the armrest dug into his kidney, but slapped his hand over Studs' ear and sent a very specific set of waves down his ear canal, just enough to lightly scramble his inner ear and make his head spin.

Studs went limp and collapsed on the floor.

"You're under arrest," Cisco panted, hauling Studs's hands behind his back. "You have the right to remain silent. Anything you say can and will be used against you in a court of law. You have the right to an attorney - "

Studs still squirmed, but by the time Cisco asked if he'd understood his rights as they were explained to him, he'd subsided, and only nodded sullenly, face mashed into the floor.

When he had Studs cuffed in a window seat in the first row, Cisco looked up to check on the marshal. She had Snake pressed against the wall of the train carriage, neatly cuffed. He was still shivering, and the ice was slowly melting from the door between the carriage and the engine.

She was on her radio, firing off codes. Cisco glanced around to check on the civilians and found them all huddled at the far end, looking at all of them - Cisco and the marshal, too - with fear and suspicion.

He sighed. Some gratitude. That was norms for you.

He looked back at the marshal, who sighed and shrugged at him before calling out, "There will be a short interruption in travel while these gentlemen are removed from the train. We should be on our way again soon."

A chorus of groans and mutters rose up, but she ignored them, steering Snake around to sit in the window seat in the row across from Cisco and Studs, cuffing him in place. She sat in the aisle seat.

"Nice job," Cisco told her across the aisle. "Marshal - ?"

"Snow," she said. "Caitlin Snow. You, too. You're CCPD?"

"Officer Cisco Ramon, at your service. Quite literally."

She shook the hand he held out. "You'll have to transfer custody, I'm afraid," she said as the train began to slow.

"Hey, he's all yours," Cisco said under the sound of the conductor making the same announcement that she had a few minutes ago. "I'm technically off-duty. This wasn't how I thought today was gonna go."

He looked around the train, still intact, at the people not lying broken and bloodied, and thought, But this is preferable.

He looked back at the marshal, whose eyes were slowly turning back to brown. The white streaks in her hair were darkening up again. She caught his eye and smiled at him, and he thought, Way preferable.

On Friday, Cisco was in his lab, bopping to the beat, when somebody cleared their throat loud enough to be heard over the music. He glanced over and saw Marshal Caitlin Snow in the doorway, and slammed his hand down on the off button.

Not only had she caught him dancing, it had been to Lady Gaga.

"Hi," he said, feeling his face go red. "Hey. To what do I owe the honor, Cai - Marshal Snow?"

"Officially, I'm here to interview you for my report," she said. "Unofficially, I'm here to thank you again. The Harknesses definitely would have gotten the better of me if you hadn't been there."

The Harkness brothers were Snake and Studs, known on their birth certificates as Jason and Bryan. "No problem. Happy to help. Is that just your thanks, or is that coming from the U.S. Marshals?"

She went poker-faced. "The U.S. Marshals' official statement is that while they are of course grateful for any assistance rendered by local law enforcement, they have a firm policy against assigning more than one meta-human to a single op. While it was unavoidable in this case, steps will be taken to ensure it doesn't happen again. For the continued peace of mind of the general public, of course."

He nodded. "Got bawled out?"

"At length."

"Same here. I mean, what are we supposed to do? Check the Eiling registry? Do a blood test?" He waved his hands. "'Ooooo, so sorry, didn't know another metagene was in the room. I'll let you handle these bad guys on your own.'"

She shrugged. "It's the price of admission."

For people like them, she didn't have to say.

He sighed. "Well, I don't get put in the field much, so it more than likely won't come up again."

"Why not?"

"Why don't I get put in the field? Uh, my powers freak some of the guys out." He waved his hand. "Anyway, I'm more useful to the department in here, building defensive equipment against metas. To tell the truth, everyone in the precinct was pretty shocked I knew my ass from my elbow in that fight."

"They must not be paying attention," she said.

He felt heat crawl up his face and changed the subject. "So - the Harknesses. What was their game, anyway? Did they just wanna create mayhem or what?"

She studied him, clearly debating on how much to tell him. "Did you notice the third car down when you boarded?"

"The one with all the power dampeners?" A lot of high-level power dampeners made you sick to your stomach. His breakfast had practically come up, right there on the platform.

"It was a federal prisoner we were transporting to Starling for incarceration. Every car had at least one Marshal on it, for just the kind of thing we prevented."

The tone of her voice told him clearly that was all he was going to get about that. "I thought you boys normally went by Con Air."

"The nature of this meta, flying wasn't an option. Anyway, the Harknesses thought they'd hijack the train and make off with him."

A cold chill rolled down his spine. "It wouldn't have worked. It would have been way worse."

She tilted her head. "You said something like that on the train. How would you know?"

"I get these flashes sometimes," he explained. "Uh. Vibes. Shots of something that's going to happen. And for the past week, I've been seeing this train leap the tracks. And everyone in it - " He grimaced. "Not pretty."

"Oh," she said softly. "But you said you were off duty."

"Yeah," he said. "I asked to be assigned to the train for the day, and they said no." He shrugged. "It crosses jurisdictions and there wasn't any obvious crime in my vibes. Just, uh, a blood drenched disaster that might or might not have happened."

"So you -"

"Took a personal day and bought a train ticket," he said.

"To board a train that you were pretty sure was going to derail and kill everyone on board."

"Always in motion is the future," he said breezily. "Clearly that didn't happen. Don't look so shocked. If I had to guess, you didn't join the Marshals for the shiny jewelry." He sat back. "Speaking of which, why doesn't the CCPD know that there's a meta stationed at the Central City Marshals' office? I mean, I usually hear about it right away when there's a new meta in our circles."

"I'm a transfer from the Coast City office," she said. "I started on Monday. I'm sure my superiors will get around to informing yours eventually."

"Yep, sounds like the cordial and respectful working relationship that we law enforcement agencies all enjoy with each other," he said.

She cracked a small smile and put her hand in her suit pocket, drawing out a metal case with the seal of the Marshals etched on the front. "Well," she said. "For what it's worth, I think we made a good team." She pulled out a card and held it out. "If you wanted to stay in touch - "

He took it, studying the front. Name, phone, email, all very official. "Maybe share information? Unofficially?"

She shuffled her feet.

He flipped the card over and found another phone number, and what looked like a personal email. His brows shot up.

She shut the case and put it away. Was she - blushing? "Or just - you know. Stay in touch."

"I'd like that," he said.

She smiled tentatively. "Yeah?"

"Yeah." He smiled back at her. "You're right. We did make a good team."