Disclaimer: I do not own Supergirl or the Flash or anything related. This is a fan created story for entertainment and no profit will be made.

Note: For the Flash's suit imagine the suit from the show with the white emblem, but brighter red with yellow boots and belt.

This story takes place after the first episode of season 2.

Chapter 1

It was a seemingly calm night in Central City. A Star Labs security guard is eating Big Belly Burger and listening to the football game while keeping an eye on the cameras. Outside a figure was approaching the door concealing a gun. The security guard noticed this and went to the front door to investigate. This proved to be his last mistake as when he was tricked into opening the door he was frozen in ice.

The figure made his way through the lab until he reached a vault. After freezing and breaking it open he found what he was after, a green glowing piece of meteor rock.

Barry Allen, CSI for the CCPD walked in looking around at the damage. His eyes quickly landed on the dead body before looking over at one the employees at Star Labs. Tina McGee, Barry's friend, doctor and the only one to know his secret. Not long ago Barry had an accident in his lab that resulted in him being changed in extraordinary ways. It has only been a month, but he has been secretly helping people as a masked hero known as the Flash.

"Tina, are you alright?"

"I'm fine Barry. I wasn't even here," she assured him.

"Barry, what took you so long," one of the detectives was approaching him. It was Detective Joe West, the father of his childhood friend Iris. He was also friends with his dad who was eliminated as a suspect in her murder due to being at work when it happened.

"Sorry Joe. I uh, got held up by traffic. It looks like it was Snart again."

"Yeah, but it doesn't make any sense. Snart usually goes for banks, paintings. So what could he want at Star Labs?"

"I can answer that detective," said Tina. "He stole a green meteor rock. It's called Kryptonite and it was sent to us to study."

"As in Superman and Krypton?" Barry was looking astonished. "You mean this is related to Superman. Something like that has been here?"

"Why would Snart be interested in something like that?" Joe took a sip of his coffee. One of the other officers at the scene commented that the Flash catch Snart. "Come on Bellows, not that again. The Flash is a myth."

Later that day at CCPD Barry was working in the crime lab. His friend and Co-worker Julio Mendez were working on another case when Tina walked in. "Hey Barry. Has there been any news?"

"I haven't heard anything yet. We'll get it back Tina."

"I know, it's just that. Some people who said they work for the government came to me with the rock in the first place. When they here about it being stolen they aren't going to be happy. I want to help, this could cost me my job and who knows what else if I don't get it back."

"Bary," Joe said as he walked in. "Snart left town for National City last night. Captain Singh wants us over there."

"National City? Where Supergirl lives?"

"Detective West, I want to come too. My job and possible future depends on getting that Kryptonite back. It was supposed to remain top secret, I can help and I won't get in your way."

"Joe, this is obviously very important to Tina. It couldn't hurt to let her tag along right?"

"Fine, but as long you don't get in our way and let us do our job."

In National City Kara Danvers was starting her first day as a reporter. After working as an assistant to Cat Grant she was heading into new territory. She was anxious but her cousin Clark was there to give her support.

She was walking into her apartment that she shared with her sister Alex to find Clark working on his laptop. She assumed he must be working on a story. "Hey Kara, how'd it go?"

"Well I got my first story, an old theater that' s about to be torn down." Clark commented that she didn't seem too exited about it. "I guess I was just hoping for something bigger."

"Kara, you're just starting out. You'll get there, you just need to work your way up and prove yourself."

"I know, you're right." Kara sighed and kicked off her shoes. "So what are you working on? A story?"

"Yeah, Lois called and told me about a criminal from Central City that arrived here in National City. She asked me to look into it. She would normally want to do this herself, but she's working on something else."

Kara had stopped paying attention at a certain point. The mention of Central City made something click in her mind. She still remembered meeting a superhero from another Earth. Barry Allen had somehow ended up on her Earth and needed her help to get home. While he was here he helped her stop Livewire and Banshee.

"Did you say Central City? Who is this criminal?"

"Leonard Snart, goes by Captain Cold because he uses a freezing gun. Why?"

Kara then told him about meeting the Flash from another Earth. He was from Central City and they both helped each other. In the short time he had been here she had come to consider him a friend.

"Parallel Earths, I've never been to one myself. To travel so fast that you punch a whole in the dimensional barrier, that's impressive. Sounds like a nice guy."

Kara couldn't help but smile. "Yeah, did you know he actually wanted to get his picture taken with my spaceship? He was so excited about the whole alien thing."

That night Snart was waiting in an alley. It wasn't long before a limo pulled up with tinted windows. The window in back rolled down and he walked up to it. "I got your rock." He handed the Kryptonite to the figure inside in exchange for payment.

"And the police from Central City. They're here looking for you."

"The deal was for me to bring you the rock. "

"I don't want them interfering. Take care of them, and you will be paid double." Snart agreed and the meeting was soon ended as the limo drove away.

Joe walked into National City's police department with Barry and Tina. They were shown to the captain's office who was expecting them. "You must be the people from CCPD. Your captain called and requested we work together to catch Snart."

"What's he doing in my city?"

"That, is what we are here to find out. He stole something from Star Labs and may have brought it here." Joe said. "His cold gun is very dangerous. You and your men need to be careful with him."

Unbeknownst to them someone could hear everything they were saying. Clark was there to get more information on Snart and his whereabouts. As they walked out of the captain's office Joe and Tina went outside ahead of Barry as he stopped for a drink. Clark saw this as his chance to approach him and get more information.

"Excuse me." Barry turned to see the stranger with glasses coming toward him. "Clark Kent, Daily Planet. I'm writing a story on Leonard Snart, he was seen exiting a plane here in National City. The lady at the desk told me you were CCPD, so he's one your's correct?"

"Daily Planet, you guys have close ties to Superman right?"

"Well, Superman has given us a fair number of exclusives. I believe we were talking about Captain Cold though."

"No this is related, if you needed to get a message to Superman could you?"

"I could find a way, what's this about?"

"Look," Barry sighed and ran his hands over his face. "I don't know if I should be telling you this. I've read your articles Mr. Kent and I know your reputation. If I tell you this can I trust you to keep it between us and only tell Superman and Supergirl? My friend's job is on the line right now and none of this is her fault."

When Clark assured him it would stay between them Barry continued, "Snart stole something from Star Labs related to Superman and Supergirl. Ever heard of Kryptonite?"

Clark suddenly got a sinking feeling in his stomach. This is what he had feared, Kryptonite ending up in the wrong hands. "Rings a bell."

"I don't know what this stuff is or what it does, but if it's related to Superman and Supergirl they would want to know about it."

"Thank you for telling me this. I'll make sure that they both hear of this. How did Star Labs get ahold of Kryptonite in the first place?"

"My friend said some government guys sent it to her for study. She couldn't have known something like this would happen, much less prevented it. Snart is smart and with that cold gun he's dangerous."

"Thank you for trusting me with this. What was your name?"

"I'm Barry, Barry Allen. I'm a CSI for the CCPD." Barry shook Clarks' hand who suddenly went wide eyed. Kara had just told him of the Barry from another earth, so this must be the one from their's. Was he also the Flash here Clark wondered.

"Barry," Joe called from the front door. "What's taking so long?"

"Sorry Joe, It was nice meeting you Mr. Kent."

"Nice meeting you." Clark watched as they left. He guessed time would tell if Barry was the Flash or not. His mind soon turned to another matter. How unhappy he was that a piece of Kryptonite had ended up at Star Labs and he didn't know about it.