Disclaimer: I do not own the Flash or Supergirl. This is a fan created work and no profit will be made.

Chapter 1

A red streak raced through Central City faster than any eye could see. Cars shook and pedestrians felt it pass by. At S.T.A.R. Labs Cisco Ramon sat watching the screen of a computer as it tracked the streak everywhere it went. His head resting in his hand as exhaustion was setting in. "Barry we've been at this for three hours now and nothing's happening. Can we call it a night now?"

Barry replied through it earpiece as he continued to run. "I've almost got it Cisco I can feel it. If Zoom can still travel to our Earth I can travel to his. I just have to vibrate at the Frequency of that Earth right?"

"In theory, but we've never done anything like this without a breach open. The Tachyon device I gave you should increase your speed enough to cross over…maybe. I know you want to stop Zoom but do really think it's going to be tonight? It's 10:30 and I'm tired man."

"It's not just about stopping Zoom Cisco. I promised that guy in the mask I would come back for him. We just left him there to save ourselves." Barry's mind wandered back to when they were escaping Earth 2. He thought about that man in the mask who tried to tell him something about Jay. "I have to get back to Earth 2 Cisco."

Barry began to push himself harder than he had ever done before. The electricity around him began to go wild. He had left Central City in no time and was now racing across the water. His speed continued to increase until finally he vanished.

National City-

It was anything but a normal day in National City. A new female superhero has just shown herself by the name of Supergirl. She was now the talk of the town as people were filled of questions of who she was and where did she come from? Soon more questions would arise as a figure in a red suit appeared from seemingly nowhere. He came to a stop in the middle of a street as the device on his chest erupted into sparks.

Barry quickly discarded the Tachyon device as he took in his surroundings. That did not last long as he heard a car coming from behind him. Acting quickly he used his speed to get out of the way. He noticed pedestrians all around him were now focused on him. He collected the device he threw off and sped away, leaving behind the confused crowd.

Some time later he was now in street clothes with his suit and the Tachyon device in a backpack he had purchased. He had decided it would be better to get out of his Flash suit and avoid drawing anymore attention to himself while he figured things out. He tried to contact Cisco or anyone that he knew but got no response. The Tachyon device was about as useful as a paperweight so he wouldn't be using it to get back any time soon.

It didn't take long to learn that he was in a place called National City and that it had it's own hero. Apparently she had only revealed herself a week ago and had just botched an attempt to help stop a fire at the port where it ended with oil spilled into the water.

Deciding that Supergirl may be his best bet on finding a way home he set about trying to find her. It was rather fortuitous that day that he happened to pass by a pizza place that was being robbed. Never being one to ignore a chance to help Barry slipped out of sight and into his Flash suit.

He sped in mere seconds before Supergirl arrived and disarmed the robber before knocking him back. As Supergirl arrived to witness this she was surprised to find the red suited stranger. He turned to face her as the victims of the robbery looked on with interest. "So you're supergirl I presume," Barry said vibrating his vocal cords to disguise his voice.

Supergirl had several questions running through her mind, but the first one she had to ask was, "who are you?"

"I'm the Flash and I'm not you're enemy. I was actually hoping to run into you. I have a little problem I thought you might be able to help me with."

This caught Supergirl's interest and decided to hear him out even thought she didn't feel ready to fully trust this strange man. "What kind of problem?"

"Not here, I hoped we could go someplace private."

"Alright, I'll hear you out. I still don't know if I trust you though."

Barry felt relieved that she was willing to listen to what he had to say. "I understand, but I hope I can change that. First we should get this guy to the police, don't you think."

After handing the robber over to the police Barry sped up onto a roof where they could be alone as Supergirl landed shortly after. "I can see why you're called the Flash. It's impressive how fast you are."

"I noticed you're not exactly slow yourself. So how did you get your powers? Was it an accident or something?"

"I'm not sure I should tell you. I still don't know you."

"Yeah right, fair enough. Anyway this might sound strange, or maybe not but I'm from a parallel Earth."

After letting that sink in for a moment Supergirl replied, "A parallel Earth? You mean an Earth that's different than this one?"

"Basically yeah, I was trying to cross over into another Earth than the one I'm from and I ended up here. The device I used to get here is pretty much broken so I was kind of hoping you might know of a way to get me back."

"I have no idea. I've never met anyone from a parallel world let alone crossed over into one."

"I see. So I guess that means I'm stuck here then." Barry's hope for getting back to his world deflated at that moment.

"I'm sorry. I wish I could help you, but I really don't know how. I'm still a little new at this."

"Yeah I noticed," Barry said catching her attention. "I haven't been here long but I heard about what happened at the port. For what it's worth I've made mistakes too. I'm sure you'll do better next time."

Supergirl smiled a little at that. "Thanks, I appreciate that. So what are you going to do?"

"I don't know. I guess for now I'll help out while I try and come up with something else."

DEO-

Kara watched as Hank Henshaw and her sister Alex looked at reports of this Flash making saves throughout National City with her. "He said he came from a parallel Earth," Henshaw finally said.

"That's what he said and I believe him."

"Kara how do you know he wasn't lying or trying to trick you. We don't know anything about this person."

"I don't think he was lying to me and he wasn't trying to trick me either. All he wanted was a way back home, but I told him I couldn't."

"I know you want to see the good in people Kara but there is no telling what this guy could do being as fast as he is. You should be careful with this guy." Alex was as perplexed about the Flash as the others. She didn't get the impression that he was an enemy but her sister could be too trusting in her opinion. "I'm not saying that we shouldn't give him a chance but we need to learn more. You didn't happen to X-ray his mask did you?"

"What? No I didn't X-ray his mask. I know a thing or two about hiding who you are so I decided to respect his privacy."

"You should find out more about him. See if he's really on our side, then we'll go from there," said Henshaw.

Later-

It was night and Supergirl was out flying. She had heard that her sister Alex had been taken and was desperately trying to find her. She noticed a red streak down below and flew down. Barry came to a stop as Supergirl landed in front of him. "I need your help."

"What's wrong," he asked.

"It's…someone I know has been kidnapped. It was an alien called a Hellgrammite. I have to find her and save he. Please help me."

"Don't worry. We'll save her." Supergirl felt relieved at that.

Barry raced down below as Kara scanned the city overhead with her super hearing. Supergirl finally located her sister and the Flash followed behind her.

Kara walked into the warehouse to find Alex lying on the ground. No one seemed to be round but she made her way over to where her sister was. "No don't, it's a trap." Alex tried to warn her but she was surprised as she was hit from behind.

"Aunt Astra? You died on Krypton. You died with everyone else." Kara was having a hard time making sense of what was happening.

"I wasn't on Krypton when it exploded. I was a prisoner at Fort Rozz, Put their by your mother."

As Astra and Kara began to fight Alex tried to radio for backup. The Hellgrammite went to attack her when Barry finally showed himself and saved her. "You're the Flash," Alex said as she realized she had been moved out of the way.

"Stay back," he said.

The Hellgrammite leapt onto a wall and at Barry and Alex. Barry rotated his arms and blew the alien away from them. As he got up Barry saw the alien open his mouth and jaw to reveal the teeth inside. Barry sped all around him landing blow after blow with his fists. He finally delivered a final punch to the face and sent the alien into a wall. The battle was over quickly as the Hellgrammite was now out cold.

Barry went to check on Supergirl and saw that her fight was over after being saved by Hank Henshaw. Alex was limping over to them not far behind. "So you're the Flash I've been hearing about." Henshaw's words were a statement rather than a question.

"That's right," Barry answered continuing to disguise his voice. "Your alien is back there by the way,"

"He saved my life sir," said Alex.

Hank nodded his head, "Nice work Flash. We'll take it from here."

"Thank you," said Supergirl. "Thank you for helping me save Alex."

Barry smiled at her and nodded in return, "Anytime Supergirl. I'm sure we'll be seeing each other around." With that he sped off into that night. Kara smiled too as she watched him go. Alex noticed this and let out a little smile herself thinking that things were going to get interesting.