Flash pulled her mask back down over her face and offered a hand up, but Killer Frost pulled herself to her feet without taking the help.

"Who are you?" Caitlin asked, as she brushed off dust from the abandoned STAR Labs and bits of rubble from that destroyed world.

"The short answer," she replied, giving up on getting it all off. She and her clothes would just need to be washed, "is I'm you from another universe. My name is Killer Frost."

Even with the mask covering half her doppelganger's face, she could easily imagine the disbelieving look the other woman was giving her. "Another universe?" Caitlin repeated slowly.

"Trust me, Caitlin," she said, "I'll tell you later, when we're back at STAR Labs."

"What about your ramp?" the speedster asked.

Killer Frost looked up in the direction Caitlin had indicated. The icy slope above their heads clung to the side of the building, curving out of sight on one side. "My powers can't reach it now," she said, "it will melt."

One of Caitlin's hands went to the side of her head, and she listened for a moment before fixing Killer Frost with a searching look. "I have to go deal with something," she said, "Cisco will be expecting you at STAR Labs." And she rushed off in a blur of lightning that was closer to white than the yellow-gold she was accustomed to seeing Flash have.

This Central wasn't as high-tech as her own, no high-speed trains, and the towers of STAR Labs seemed to be more damaged than usual, but there had been extra security added. The sensors at the doors of STAR Labs wanted her thumbprint, and the light beeped green when she gave it, but thankfully the security didn't care about her eyes. Though she had the same fingerprints as Caitlin, the ice in her eyes would confuse a retinal scanner.

"So," Cisco spun around in his chair when she walked into the cortex, pointing the straw from his drink at her, "you're Caitlin from another universe?"

"More or less," Killer Frost confirmed. She had been Caitlin once, before her life changed so drastically, but the genetics would still say she was Caitlin, no matter what her name was. The engineer gave her a befuddled look, but he didn't have time to comment, because then Flash stopped next to her in a rush of wind and lightning, and Cisco almost dropped his orange soda all over the floor, looking back and forth between them.

"I have got to stop making plans on Tuesdays," he said finally, "everything crazy starts on Tuesdays."

"Which is why Barry and I have date night on Wednesdays," Caitlin said matter-of-factly. She leaned her hip against the edge of the desk, crossing her arms, and turned her attention from Cisco to Killer Frost. "Another universe?" she prompted.

She shifted her weight, wincing a little as the motion pulled at the side she'd landed on. Pressing one hand gingerly to her ribs, she let ice creep across her skin under her shirt. "I fell through a breech, a fissure between the universes," she explained, "and wound up here."

"Prove it," Caitlin said.

"Your print scanner let me in," Killer Frost replied, "If your version of Barry Allen is anywhere near as involved as he's been in some of the others, you know the odds of the same print coming from two different people. If you want to check, you and I have the same DNA too."

Her doppelganger didn't looked convinced, but Cisco turned around and started typing on the computer, pulling up what was probably the logs for the doors.

"Her prints match yours, Caitlin," the engineer confirmed, "either she's telling the truth or she's a perfect copy, which," he added to her, "would be really cool. Kinda freaky, but cool."

In a flurry of the white lightning, Caitlin sped out of the room, returning seconds later with a large sheet of paper that she laid down across one of the other tables. "Assuming you're telling the truth about the breech," she started, and Killer Frost crossed over to see she had a map of Central, "you came through here." Caitlin touched the spot where the breech had opened, and looked up at her. "Where were you on the other side?"

Killer Frost pulled one of the chairs around the table and took a seat. "The locations usually match on either side of the breech." A flick of her fingers raised a skyscraper out of ice on the map where Caitlin was pointing. "I went through above there, so that's where I came out. There's also one in the bank and in STAR Labs, and I'm sure several more."

Her time in this universe would be easier if the speedster didn't mistrust her so much, and she wracked her brain for something to prove what she said. "Barry likes to sing while he works," she told Caitlin then, quiet and only for her ears, "but only when he thinks no one can hear, and Cisco was disappointed that he didn't get to give Hartley Rathaway a code name, even though he approved of the name Pied Piper."

There was silence from her doppelganger, and when Killer Frost looked up, she found Caitlin looking at her. For a moment, their gazes held, then Caitlin smiled, a small thing that just curled the edges of her mouth, and nodded. "I believe you. I just had to be sure. Everyman fooled us twice, and Barry was tearing himself up about Wells after he betrayed us."

"The bank and STAR Labs, you said," the speedster changed the subject, bending back over the map, "What about the one you just came out of?"

"Those are the ones I've been through consistently," Killer Frost replied, "Central City in the universe I just left had been destroyed, the only portal correlated to that-"

Her explanation was interrupted by a rap from the hallway and Barry called out, "I brought lunch."

She looked up and he was standing in the entrance to the room, holding up a paper bag and watching the occupants with a smile on his face. Abandoning the map, she started to go to him, only to halt before she even stood up as she remembered that if Caitlin Snow was the Flash in this universe, Barry Allen was not a speedster.

"Caitlin?" he asked, even as he set the bag on the desk near the computers. He sounded unsure of the identification.

"Killer Frost," she corrected.

There was a flicker of lightning at the edge of her vision, the paler white-gold she was starting to associate with her doppelganger, and Caitlin halted beside Barry, tucking flyaway strands of hair behind an ear. "Barry, this is Killer Frost," she said, "Killer Frost, meet Barry."

"Okay," his gaze kept flickering around the cortex, jumping from person to person, even as he reached out to take her hand, "why does she look exactly like you?"

"She's Caitlin from another universe," Cisco called across the room, "Not the weirdest thing we've seen all month. Did you tell them no mustard?"

Barry pressed a kiss to Caitlin's cheek, the gesture quick and casual, then turned to root through the bag, pulling out burgers. "Here," he tossed one underhanded to Cisco, who caught it with practiced ease, "onions and no mustard." He handed another to Caitlin, then turned, and Killer Frost only just caught the one he tossed to her. It was still warm and she hadn't eaten in- she didn't actually know when she'd last eaten, several universes ago, but she hadn't realized how hungry she was until she tore in.

Between bites as they all ate, Barry was filled in with everything Cisco and Caitlin knew, and she filled in what she was willing to tell them at the moment. Somehow, she didn't think that revealing an alternate version of the man her doppelganger was dating had sent her to kill speedsters would go over well.

"And I desperately need a shower," she concluded, licking grease off her fingers, "if that doesn't impose too much."

"Nah," Cisco stood up and went into the other room. "Little help," he called out after a second, and Killer Frost went to go see what it was.

He had opened a closet in the treadmill room, and was tugging on a box wedged between the frame and the shelf. She reached up, careful not to touch him, and pulled on the other side, and together they got it onto the floor, where Cisco made short work of untucking the flaps where they had been neatly folded over each other. "I knew these would come in handy someday," he said, standing up with a bundle of grey fabric in his arms. He piled this into her arms.

"Clothes," he told her, "there should still be towels and soap in the bathroom, down a level, in the hall to the right."

After a few wrong doors, she found the bathroom Cisco had mentioned. She shut the door, looked up, and found herself staring into a mirror.

The first time she had seen herself after she received her powers, she had freaked out at seeing a stranger reflected there and broken the mirror. She still wasn't sure if it was the ice or the flailing hit that had cracked the glass. Zoom had never been big on pictures, or mirrors, so it had been easy to avoid looking at herself after that time.

Her reflection didn't seem so strange now. She was paler than she had been before her powers, her lips white, or a very light blue, and her hair blonde. The biggest change though, was her eyes. She knew the ice in them had turned them blue, but she hadn't known that ice glinted in the light, changing to white in places as the light caught it differently.

The clothes, it turned out, were grey sweatpants and a similar sweatshirt with the STAR Labs logo on the front. Both were slightly too large, but much cleaner than the clothes she had been wearing. Those she ran under the water, then hung up to dry. It wasn't perfect, but in lieu of a washing machine, it would do.

"Using the data Cisco scanned from the breech in our basement," Barry was saying as she walked back into the cortex, "which is not a sentence I ever thought I would say, we developed a detection program to find others."

"We found a couple more," Cisco added, "but they keep fluctuating. The program's still running, so we'll find them all eventually, but for now we have four."

"Is there a way to seal them?" Caitlin asked, leaning over Barry's shoulder to look at the computer screen.

"Seal them?" Killer Frost repeated, making the inhabitants of the room jump.

"You said you fell through," the speedster answered, "but you're a meta-human, we don't know what the trip would do to someone without powers. Even if it doesn't, duplicates of people walking around could only create confusion."

"If we could shoot a pulse of exactly opposite frequency," Cisco said, looking up from the paper he was scribbling on, "we could create destructive interference and force the breech to close. It would require very specific wavelengths though."

She tuned out of the conversation as they started debating various ways to close a breech. If they closed the breeches, would that stop all travel between universes, or would it just seal them off at this end? Either way, she had to go through before they closed the last one.

After a while, Cisco stood up from the table and went to his workbench in the other room. Killer Frost trailed after him, leaning on the table and watching him fiddle with bits of metal and wires, not really making anything, just moving his hands so he could think. It wasn't terribly exciting, but it was slightly more so than sitting in the other room watching Barry pace and Caitlin drum her fingers, though she could still see that too through the glass.

"I take it they're not," Cisco made a gesture back in the direction of Barry and Caitlin that was probably meant to encompass the entirety of that relationship, "in your universe."

She made a noise that might be trying to pass for a laugh. Her relationship with Zoom was similar and yet so very different from what this Barry and Caitlin had that it was laughable. "The version of him in my home universe is called Zoom," she told Cisco, "and we were lovers, but we weren't-" she made a similar gesture to the one he had made, "that."

He accepted that with a shrug. "He's Zoom, you're Killer Frost," Cisco commented, without looking up from where he was turning a screw, "I wouldn't get to give anyone a code name in that universe. Hand me that set of pliers? The ones with the red handles."

Killer Frost set the tool he'd asked for into his outstretched hand.

There was a clatter as both tool and the device being wired hit the table, and Cisco made a gasping sort of sound. Her gaze whipped over from where she'd been staring into space to find him with his eyes wide and mouth gaping open, looking like someone had just electrocuted him. He stayed like that for a heartbeat, then he rocked the table as he toppled off his seat.

Her first thought, ridiculous as it was because she knew she hadn't taken any heat, was that she had iced him, and she scrambled around the table to check, calling his name.

He was breathing like he'd just sprinted a lap around the labs, and looking at her like she had sprouted horns. "I saw- alley- you- Barry-" he gasped.

In a whirl of lightning, Caitlin was on Cisco's other side. "What happened?" she asked, hands probing gently at his head, checking for -injury.

He shook the speedster off. "I vibed, off her," based on the way Barry, in the doorframe, immediately straightened at those words, it meant more than just a general feeling, "I saw Barry, in a costume like yours but black, kissing her in an alley."

Her heart sank as she realized what was happening. Somehow, he knew about Zoom, about the reason she had started traveling between universes. "He told her to kill the Flash, and she said yes."

Caitlin moved in a rush, speeding over Cisco, and she felt the speedster crash into her almost at the same time she felt her back slam against the opposite wall. A tiny part of her noted, almost absently, that Cisco had been wrong; the universe wouldn't end if she touched her doppelganger.

"Why are you really here?" the speedster demanded, "who sent you?"

There was no reason to hide now. "Zoom," she choked out, as the elbow in her throat pressed a little harder, "sent me to kill the Flash, but I couldn't. Not in that universe, or any since. The only one I could kill was Reverse-Flash, when he threatened my life. I swear."

For a second, she wasn't sure whether Caitlin was going to release her or not. The speedster scrutinized her and even without the elbow in her windpipe, she would have had trouble not holding her breath. Then Caitlin jerked away and she fell to the floor, coughing and taking deep gulps of air.

Someone, not warm enough to be a speedster, patted her forcefully on the back, and she nodded gratefully. It took several more coughs before she felt coherent enough to look up. Barry was crouched next to her, but Caitlin was hovering close on the other side, ready to react if she did anything. The idea was nearly laughable. She'd had dozens of chances since walking in here to do whatever harm she might have wanted to, and she was hardly going to start now.

"What's your gift?" she asked Cisco, looking past both of them to the engineer leaning against the table. He still looked paler than usual, but she didn't know if that was from the use of his gift or from what he'd seen. She didn't think Zoom was terrifying enough to prompt that extreme of a response, so she would guess it was the first one.

Cisco snorted. "More like a curse," he grumbled, "I can't control when the visions come."

"Sometimes when he touches people, or objects that were close to them, he sees things about them," Barry explained, "With you he saw the past, but sometimes he sees the future, sometimes the present. Dr. Wells described it as 'seeing through the vibrations between the timelines' before-"

Her mind seized on one of the words. "Objects?" she interrupted.

Barry nodded. "Yes. Helmets, weapons, things their owners had for a while."

"Like this?" She drew out the emblem she'd taken from Reverse-Flash and held it out toward the engineer. She didn't know if this would work, if it would even show him what she'd done to Reverse-Flash, but it was worth the shot.

Cisco reached out in a manner more reminiscent of the way someone would usually touch a live piranha than an inanimate object, and laid his hand on it. The shock was written across his face again as he gasped, and then it was over.

"I saw her kill Reverse-Flash," he confirmed, "she made sure Barry was okay, then left."

He looked at her one more time, then turned and strode out of the room.

"I'm not going to hurt you, any of you," Killer Frost told Caitlin. Her doppelganger looked like she was wavering, biting on her lip. "I had plenty of chances and I didn't. I just want-" she had to stop as she realized she didn't have a mission anymore. She had completed the one Zoom set out for her, and all that was left was- What? If she sat still long enough, maybe Zoom would come and get her, or maybe when she wasn't in the universes he'd left her in, he'd stopped looking. She didn't know, but-

"I just want to go home," she finished finally, "but I don't know how to do that anymore."

Caitlin chewed on her lip more and swapped a look with Barry that had a whole silent conversation in it. He nodded, and Caitlin reached down, offering her a hand back up.

"Help us close the breeches," she said, "and we'll see what we can do about getting you home."

Killer Frost nodded her agreement, not completely trusting her throat to speak.

By the end of the week, her bruises had faded from purple and blue to green and yellow, they had located all the breeches, and Cisco and Barry had come up with some sort of device that should close them. They had almost scrapped the design when Barry pointed out they had to channel way too much heat for the materials they would have to use, until Killer Frost countered that she could cool it back down.

And they'd discovered that the breeches only activated if Killer Frost or Caitlin went near them. The first theory was that they reacted to meta-human powers, but every single one remained stubbornly dormant when Cisco was nearby, and Barry asked a favor of one of the meta-humans they'd rehabilitated and remained on friendly terms with to get her to try. She teleported straight through the space where the breech was, but it didn't so much as quiver, let alone open a portal to another universe.

"Maybe it's just Caitlins," Barry suggested from where he was sitting on a crate, making final adjustments to the device they'd built. They had decided to start with the one on the docks, given that if something went wrong, this one was furthest from buildings and people were least likely to get hurt.

Killer Frost shook her head, not looking up from the miniature snowman she was building in the palm of her hand. "Zoom took me through, the first time," she reminded him, "and it opened for him."

"But," Cisco surfaced from his toolbox with a noise of triumph, holding a set of batteries that he started fitting into the control box, "it can't just be speedsters, because it opens for you."

She shrugged, and set the finished snowman into the line of miniature snowmen she was stacking along the edge of the crate they had put the machine on. The first one was starting to melt under the bright sun, leaving a spreading wet patch on the wood, and the others were in various state of decay.

"Ready?" Caitlin skidded to a halt next to the crate in a rush of air and static.

Cisco snapped the panel back into place and hopped to the ground. "Yep."

"Wait," Barry leaned over and kissed the speedster, very quickly, "For luck."

Caitlin smiled, small and almost shy, then pulled her mask up. In a rush of white lightning, she took her place by the breech, which flared open at her presence. "Ready!" she called out, and Cisco hit the button as she started doing laps around it, holding the breech open at the same size while the device calibrated and then, in theory, sealed the breech.

For the first ten seconds, everything worked perfectly, then the machine started whining.

"It's overheating!" Cisco shouted over the rush of sound and the whine of the machine, "do your thing Frosty!"

Glaring at him for the new nickname could wait until they weren't in danger of exploding. Killer Frost flung out both hands, pulling heat from the machine desperately. It glowed under the strain and started whining, the pitch growing higher and higher until with a small roar, the breech writhed, once, twice, then imploded, sucking them, several crates, and the entire contents of Cisco's toolbox toward it.

Someone started laughing, and then they couldn't stop, relief it had worked and fading adrenaline making the whole thing funnier than it would be otherwise. Eventually, they calmed down, picked themselves up, and Cisco went to check the device while Caitlin figured out if any of the surroundings had been damaged, leaving her and Barry to gather the scattered things that Cisco had been keeping in his tool box.

Killer Frost was reaching between two crates, chasing the last spool of wire that seemed determined to roll away from her when Barry set the box down next to her. "I think that's-" he broke off as she turned, producing the wire with a victorious flourish that she knew didn't reach her face, "What's wrong?"

She pulled her gaze from the handful of tools to Barry's concerned face. "If I don't go through before we close them all, I'll be stuck," she told him.

"You could stay here," Barry suggested, "if all the breeches are closed, Zoom can't reach you in this universe. You'd be safe, you could be whoever you wanted to be."

Killer Frost looked away, out over the water. Seeing him like this, with this Caitlin, reminded her a little of the way things had been with Zoom. She wasn't sure anymore if he had been in love with her the same way she had loved him, but he had cared for her when everyone else was afraid of her.

There was always going to be a part of her that loved him for that. She owed him enough that she had to find him. If nothing else, she could close the breeches in her home universe to stop him. She would deal with whatever came after that when that came.

"No. I can't," she replied, "I'll go through the last breech." And, all things told, it hurt to watch Barry so close and yet totally out of reach. Zoom's solution, she knew, would have been to kill Caitlin, but she refused to consider that as an option. "I loved him, or maybe I still do, I don't know, but someone has to stop him, and I know him best. If I can't reason with him, worst case, I can close the breeches in my universe and seal him in."

"What about you?" Barry asked.

She glanced back at him and managed to smile. "I can handle Zoom," she said, "I was around him for months and I'm fine, which is longer than anyone else."

He reached out and squeezed her shoulder, and she covered the hand with her own, very carefully not freezing him. Even without the heat a speedster generated, he was still warm in a way that had nothing to do with temperature. Replacing the tools, Barry lifted the kit and they went to join the other two.

The rest of the breeches were closed with varying degrees of without-a-hitch. The size of the implosion, they quickly discovered had nothing to do with how wide the breech was or how long it took to seal it, and they learned to hang onto something immobile after Barry got thoroughly scraped up being dragged along the pavement toward the closing breech

Halfway through, the machine needed repairs, Caitlin needed to eat something, and Killer Frost needed a break, so they all trooped back to STAR Labs. Caitlin did a food run, Cisco did repairs, and they shut the breech in STAR Labs over lunch before heading out again.

It was the middle of the afternoon when they reached the last breech, in an alley near downtown, and Killer Frost stopped and just stared at it. Her presence nearby made it flare into life

Barry pulled the bag that he had retrieved from STAR Labs off his shoulder and handed it to her. "This has your stuff, blueprints for the breech-closer, as well as notes from each of us to ourselves that you can use to persuade that you are who you say you are."

Very quickly, so she didn't freeze anyone, she hugged him, and then Cisco. There was something a little awkward in hugging your own doppelganger, so she shook hands with the Flash instead.

She cooled the breech-closer, which they still hadn't come up with a better name for, and took the last few steps toward the breech. Cisco flipped the switch on the breech-closer, and the breech started to shrink.

"It was nice to meet you," Caitlin called after her, and there was not a trace of anything but honesty there.

"Likewise," Killer Frost replied, and ran the last few steps, leaping through the breech. She felt the jolt as it shut rattle her teeth a few seconds later, then she was lost to the blue.

Information for the universe.

Eobard/Wells recruited Barry to work at STAR Labs, to keep a better eye on him. So Barry was there the night the particle accelerator exploded and the lightning that was supposed to hit him hit Caitlin instead, making her the Flash. She woke up nine months later to find that only Barry and Cisco hadn't deserted Wells, who was not very happy that his precious future had been changed.

So I meant to have this out yesterday, and then my computer decided to restart and I redo a bunch of it. Thanks for reading, hope you enjoyed. Next chapter will be up soon.