Hello, and welcome to 'The Earth-1 Factor', an alternate version of 'Medusa' in which we actually get a crossover! All that hype about an Epic Four-Night Crossover Event, and then we get a normal Supergirl episode plus 2 random breaches that don't affect the plot in any way whatsoever plus a tiny scene with Barry and Cisco at the end that gets re-shown in the Flash part of the crossover. You could skip 'Medusa' and still understand the crossover perfectly.

This series does fit into my 'Long Way Home' series, but you don't have to read the rest to understand this. All you need to know is that in this series, there is NO FLASHPOINT. Cisco isn't hating Barry right now, Baby Sara still exists, and the Dominators were going to come, regardless.

DISCLAIMER: I don't own Supergirl or The Flash.

WORD COUNT: 5726

Saturday, November 26th, 2016

Supergirl flew as quickly as she could to the L-Corp building. She had to get there before Henshaw did, to warn Lena about the isotope. She could not let Cadmus get their hands on it, could not let them stabilise the Medusa Virus, or else all the aliens in the city, aside from herself, would suffer and die. Or else Mon-El, who was already infected, would continue to suffer and eventually die.

Sadly, Henshaw had already beaten her there. Supergirl caught the security guard that he'd thrown into the air and landed as gently as she could, setting him on his feet. The man didn't need to be told to run away as fast as he could, getting out of the lobby and away from the alien and the cyborg as quickly as his legs could carry him.

Henshaw pulled the hood of his jacket back, fully exposing the metal covering half his face. It still unnerved Kara to see the face (one of the faces) of the man who was like a second father to her (well, third, actually), glaring at her with such hatred. "I shoulda known you'd show up," he snarled.

The two of them charged forward and slammed into each other, the sound rattling the windows, both fighters grappling for dominance. Supergirl managed to knock Henshaw (she absolutely refused to call him 'Cyborg Superman') back a few steps by repeatedly punching him in the chest, and landed a few more blows, until he grabbed her arm and threw her into the large, decorative stone sculpture of the L-Corp logo.

Dazed, Supergirl sat up, and saw Lena Luthor standing in a doorway, looking shocked and terrified at the sight before her. That terror only increased when Henshaw picked up a large, broken-off piece of the statue and hurled it at her.

Supergirl got in between Lena and the huge chunk of stone as fast as she could; it shattered into dust and hundreds of tiny fragments upon impact with her Kryptonian body. "Get out of here!" she told Lena before flying at Henshaw.

Unfortunately, the cyborg just reached up and caught her, and with nothing solid for her to brace herself with, Supergirl found herself being slammed into the floor, one of Henshaw's hands holding her down while the other gripped her wrist.

She heard men's voices sounding and gunfire erupting; the police had shown up.

"All this time trying to save the world," Henshaw growled, completely ignoring the bullets pelting against his back as if they and the cops weren't even there, "who's gonna come and save you? No one's comin' to your rescue." Supergirl struggled to free herself from his grip, but he was just as strong as she was, his hand clenched around her wrist like an iron vice on a normal human.

Suddenly, Henshaw looked over his shoulder and let go. As he stood up, Supergirl got a clear view of what had caught his attention. A swirling blue portal had appeared in the middle of the L-Corp lobby. Even the police officers had stopped in their firing to gape at it.

It was just like the one that had opened over the dinner table two nights ago. And just like the one she saw last summer, when…

Two figures suddenly emerged from the portal: one in jeans and a hoodie with some weird, glowing goggles over his eyes, and one wearing a very familiar red leather suit and cowl with a small lightning logo on his chest.

"Flash!" she gasped, relieved to see her speedy friend from a parallel universe showing up right when she could really use a helping hand.

"Who the hell are you supposed to be?" Henshaw growled, for once sounding like he was actually confused by this turn of events.

The guy in the goggles gulped as he looked around and took in his surroundings. "Is this a bad time? 'Cause this is really looking like this is a bad time."

Supergirl took advantage of Henshaw's distraction and swept his feet out from under him, and then stood up. "No, actually," she disagreed, "Your timing couldn't be better."

Henshaw sat up and fired a blue laser beam from his robotic left eye, aiming at the newcomers. The Flash grabbed his friend and pulled him off to the side at super-speed, depositing him behind the cops before circling around and running at Henshaw.

Which turned out to be a terrible idea, as he basically bounced off the cyborg with a loud clang that had everyone else wincing, and rolled several feet before coming to a stop.

Supergirl winced, even as she kicked Henshaw in the face. "Yeah, you might not want to try that."

"Noted," Flash groaned. At least he was still conscious, which was always a good thing.

Deciding that he would be okay, Supergirl turned her attention back to Henshaw, who had gotten to his feet. She dodged two punches before dealing two of her own, sending him stumbling backwards.

Unfortunately, Henshaw's next move wasn't directed at her. His eye laser shot out again, this time to hit the stone ceiling, specifically the lower section directly above all the cops and the Flash's friend.

Supergirl rushed to the rescue, pulling as many officers as she could out of the way. Kara caught a red blur and flashes of yellow lightning out of the corner of her eye, which told her that the Flash was pitching in to help, as well.

Luckily, they got all the cops out of the danger zone – including Maggie, who stood out with no protection besides a bulletproof vest compared to all the other officers in full SWAT gear – as well as the Flash's friend. Supergirl looked around, but she couldn't see Henshaw anywhere. He'd made himself scarce while she and the Flash were distracted.

"Damn it!" Maggie cursed, "The bastard got away!"

"Well, that was fun," the Flash muttered sarcastically, rubbing his shoulder where he'd slammed into Henshaw, "I think I dislocated something."

"You should've gone for the supersonic punch," his friend suggested, "Like what you did with Girder. Back when he was alive, I mean, not Zombie Girder. That was different."

"The supersonic punch still broke my hand."

Maggie raised one eyebrow. "Zombies? Do I even want to know what you guys are talking about?" she asked, "Also, who the hell are you?"

Supergirl stepped in. "Ah, this is the Flash. He's a superhero from… well, another Earth. In a parallel universe, I mean. And I'm guessing his friend here is…"

"From the same Earth," the guy confirmed, "Call me Vibe."

"I guess we should count ourselves lucky that you didn't pop out of that first portal I saw on Thursday. You would've landed right on our Thanksgiving dinner. Literally right on top of it."

Vibe winced. "Yeah, sorry about that. We sorta knew it'd take a few tries to get it right."

"What are you guys doing here, anyway?" Supergirl asked, "I mean, I'm grateful for the help, but something tells me that that's not the reason why you popped by."

"We kind of need your help with something," Flash admitted, "But it seems like you've already got your hands full with your own crisis, here."

Supergirl sighed. "There's this evil organization called Cadmus that has gotten their hands on the formula for an anti-alien bio-weapon that could kill all the aliens in the city. That guy I was fighting just now was their toughest enforcer."

Flash nodded seriously. "Need a hand?"

"I don't want to take you away from whatever you're dealing with."

"No, it's okay. I mean, I'm not the only hero working on it. Besides, time seems to flow a bit differently between our Earths. The last time I was here, I stayed for pretty much an entire day, but I was only gone from my Earth for less than a second."

"It's true," Vibe confirmed, "We were monitoring him the whole time during the speed tests we were running, and we didn't even notice him going anywhere. All of a sudden he was just asking us: 'How long was I gone?!'"

"I don't understand any of this," Maggie sighed, shaking her head.

Supergirl smiled. "There's a lot to explain. How about you meet us at the DEO building and we'll fill you all in?" By 'all', of course, she meant Maggie, Flash, and Vibe. She wasn't counting all the other officers Maggie had brought with her, since she was pretty sure they didn't have clearance.

"Race you there?" Flash asked her with a grin.

"Actually, we've moved bases since the last time you were here; the DEO is now located in a nice, clean skyscraper in the city instead of that dirty old cave out in the desert."

"I thought the desert base was kind of cool."

"Clearly, none of the bats bit you during your brief stay." True, the bat that had tried to take a chunk out of her had obviously come off worse due to her Kryptonian invulnerability, but it was the principle of the thing!

Kara was rather embarrassed to admit that she had been beaten in a race in which only she even knew where the finish line was. Barry had followed her to the new DEO headquarters, and then had put on a sudden burst of speed once he knew where he was going and ran up the side of the building, getting to the balcony less than half a second before she did.

"Do you think your friend will be annoyed that we left him to ride with Maggie?" Kara asked casually as she landed next to him (partially to change the subject and distract him from gloating over his victory).

"Maybe. But Cisco doesn't really like it when I drag him around at super-speed, so he probably won't be that upset. This is a nice setup you have here, by the way."

"I know, right? I wish we'd been operating out of here last year. They didn't even tell me about this place until July, a few days after you left!" She spotted Alex and J'onn approaching, both looking wary of the stranger who'd arrived with her. "Okay, I'd better introduce you. Barry, this is J'onn J'onzz, the director of the DEO, and my adopted sister, Alex Danvers. J'onn, Alex, this is my friend Barry, aka the Flash. Remember, I told you guys about him visiting our dimension while the two of you were hiding out?"

Alex nodded. "He helped you with Livewire and Silver Banshee, right?"

"Yeah. He and a friend showed up at L-Corp when I was fighting Henshaw. That portal over the dinner table on Thursday was their first attempt. They were a big help, and Maggie's giving the friend a lift here."

A faint blush briefly appeared on Alex's cheeks. "I'll go downstairs and wait for them, and let the security team know she can bring him up." She hurried off, leaving J'onn with Kara and Barry.

Barry was staring at J'onn. "You know, you look a lot like the guy we were just fighting…"

"J'onn's a Martian shapeshifter," Kara explained, "He took on Hank Henshaw's identity a long time ago, back when he was thought to be dead – it's a long story, but now the real Henshaw's back, and he's evil, and he wants to wipe out all aliens on the planet."

"Barry!" The delighted cry drew their attention to Winn, who was running up the stairs with a big grin on his face, followed by Eliza. "Dude! You're back!"

"Hey, Winn," Barry greeted him with a grin, pulling his mask off.

"You totally showed up just in time! We're kinda on the verge of a possible alien genocide happening city-wide, and we could use all the help we can get."

"Who is this?" Eliza asked.

"Oh, I'm Barry Allen," Barry introduced himself, holding out his hand for her to shake, "I don't know if Kara's mentioned-"

"The man from another universe with super-speed powers? Yes, she spent a whole hour telling me about it." She then turned to Kara. "Did you secure the isotope from L-Corp?"

Kara sighed. "No. No, but Henshaw didn't get it, either." The five of them began to make their way down the stairs into the base proper. "How's Mon-El?"

"He's not getting better, Sweetie, and we're no closer to a cure."

"There's gotta be something on that crystal from the Fortress that'll help."

"So far, there's plenty describing how to synthesize and disseminate the virus," Winn responded, "but I… I don't think they ever even considered a cure."

"What about Lena Luthor?" Eliza suggested.

The question brought Kara to a halt, and she stopped and stared at her foster mother in confusion. "What about her?"

"Lena's mother took the Kryptonian virus and synthesized it on Earth. If Lena is working with her-"

What?! Eliza couldn't be suggesting what Kara thought she was suggesting. "Lena was shocked to see Henshaw. He would've killed her, too."

Winn seemed skeptical. "Eh, Luthors are pretty good actors, or, well, sociopaths, either way, they- they know how to fool people."

Kara turned to Barry. "Can't you help me out on this one?"

Barry held up his hands. "Hey, I've never even heard of this Lena person. I can't weigh in on a subject I know nothing about."

"Lena Luthor is the adopted sister of Lex Luthor, an evil supervillain on this Earth," Winn said bluntly, "And her adopted mother Lillian Luthor's the one behind this whole alien virus plot. The whole family's bad news."

Kara shook her head, refusing to believe that they were all leveling these accusations at her friend. "No, no. I looked into Lena's eyes. She doesn't know anything about Cadmus and her mother; I know it."

But it was J'onn who went for the gut-punch argument, the armour-piercing question: "Would you stake Mon-El's life on that?"

Apparently, the answer to J'onn's question was 'No', because Kara soon flew off to talk to Lena Luthor and to try and get some information from her, leaving Barry alone at the DEO with her team. Cisco arrived not long after that, along with Kara's cop friend, Maggie, who immediately walked off to talk with Alex.

"She kept asking me questions the entire way there," Cisco complained, "It was like being in an interrogation room in a cheesy cop movie, with the Bad Cop leaning over you and constantly getting into your personal space, and screaming at you – well, she wasn't actually screaming, but you get what I mean."

Barry shrugged. "We showed up through an inter-dimensional portal. People are going to be asking lots of questions. Besides, you're the one who didn't want me to run you over here."

Just then, Winn came up to them. "Hey, guys, uh, J'onn wants to talk to you two. I think he has a few questions about what you can do and how you can help."

Barry and Cisco glanced at each other and shrugged. "Yeah, sure."

Winn led them up to what had to be the DEO's main command centre, on the same floor as the balcony Barry and Kara had arrived on, featuring a ring of computers – some being used, some unattended – and a round, metal table in the middle. Winn went and sat down at one, getting straight to work. J'onn the Martian Shapeshifter (and wasn't it awesome that an alien openly held the leading position in a secret government agency?) was reading something on one computer monitor over the shoulder of an agent, but he straightened up and walked over when he saw Barry and Cisco. "Gentlemen, just the people I wanted to see. I was hoping you could tell me a little more about yourselves before I let you get involved in our operations any further. For security's sake, I mean."

Nearby, Winn was doing a horrible job at pretending to not be listening in.

Barry shrugged a third time. It wasn't like they were planning on keeping secrets from the people that Kara trusted. "Yeah, we kind of figured you'd ask that. So, uh, about three years ago on our Earth, there was a huge Particle Accelerator being turned on in Central City, where we lived, created by S.T.A.R. Labs."

"I worked for S.T.A.R. Labs even then," Cisco cut in, "And I was actually in the building when there was a malfunction – which we now know was actually sabotage – and the Accelerator blew up."

"There was also a storm going on that night, and I was struck by lightning, and was in a coma for nine months, and I woke up with super-speed powers. Cisco and the rest of the S.T.A.R. Labs crew have been helping me get a handle on them, and we've been working together while I run around saving people."

"Because Barry wasn't the only one who got powers that night; people all over the city were affected, including a lot of people who were already criminals. Although some powers didn't show up for a long time. My powers took more than a year to start appearing, and our friend Caitlin just developed her powers in the past couple of weeks."

J'onn looked at him curiously. "And your powers are…?"

"Oh, I can 'Vibe' things, meaning I can touch something that belonged to somebody else and get visions, and sometimes they just happen without any trigger – that's annoying, and those ones always seem to be the scariest. But they're pretty useful. And I can also open breaches between worlds, which is how we got here, and I can do this sort of vibration-blast thing, which is wicked-cool, but I prefer to stay on base and do the tech thing instead of going out and fighting."

J'onn nodded, giving them an intense look that had Barry feeling like he was being x-rayed, or something. He wondered if Martians could also read minds. "All right, then. And what, exactly, was your purpose coming here?"

Barry sighed. "We're possibly facing an alien invasion," he admitted, "And that's something our Earth isn't used to, or prepared for. I mean, we've got meta-humans and magic, but if we also have aliens living on our Earth like you have on this one, it's not public knowledge. Our contact in this secret agency called A.R.G.U.S. – actually, she's the director, now – says that the US government has it under control, but we're not sure. We've gathered up a lot of other heroes to help if it comes to a fight, just in case, but I figured Kara would be a good source of assistance, being the only alien I actually knew."

Thankfully, that talk seemed to satisfy J'onn's concerns. Cisco and Barry tried to make themselves useful by looking over the data on the Medusa Virus, but sadly, they found themselves out of their field of expertise and couldn't figure out anything that the blonde woman Barry met earlier (who turned out to be Alex's mother, Dr. Eliza Danvers) and Alex herself hadn't already determined.

Kara returned soon after, vehemently saying that her talk with Lena Luthor had turned up no useful information; if anything, she'd only succeeded in offending and hurting her friend. She went to sit at the bedside of Mon-El, an alien friend of hers who'd been infected with the virus.

Meanwhile, Barry and Cisco passed the time while talking to Winn.

"Okay, so… if I'm like a combination of Cisco and this Felicity girl, who do you think… Alex is more like?"

Barry and Cisco both tilted their heads in thought. "Well, considering her science chops, more specifically biology, I'd say she's a lot like Caitlin, but then she's also a kick-ass secret agent, so… Sara?"

"More like Lyla," Cisco corrected, "She actually runs her own secret agency, whereas Sara was trained by an ancient order of assassins."

Winn blinked. "You guys have some very interesting friends."

"Says the guy who works with aliens on a daily basis."

It seemed that, on any Earth, insistent, high-pitched beeping was never a good sign. "What is it?" Kara asked as Winn all but dove for a chair in front of one of the computers.

"Radio-electrical alarm. Isotope 454 has a radioactive signature, so I set a program to alert us if it was ever moved from the stockpile at L-Corp, and…"

"Let me guess," J'onn said, having joined them, "It's moving."

"And how. Looks like Cadmus is preparing to release the virus at the port of National City."

"What?" Kara questioned. "Why? The port isn't a drinkable water supply."

"It's the perfect place to launch the virus into the air," J'onn theorised, "and disperse it across National City."

Suddenly, all the screens in the DEO's mission control room abruptly filled with static, a computer-generated face appearing a split-second later. "Tonight, our nightmare ends," a synthesised feminine voice said, "Tonight, every alien who has set foot on our planet will die. Because Earth is for the humans. The future is for the humans. We are Cadmus." The screens flickered once before returning to their original display.

"Well, that was creepy," Cisco commented.

"We have to move," J'onn ordered, "Right now."

"Call Alex and get a strike team to meet me and Barry at the port," Kara told Winn, who immediately went back to his computer to do so.

"There's no time, Supergirl," J'onn countered, striding towards the exit while Kara and Barry hurried after him, "It's just you and me and Allen."

"J'onn, you can't go out there," Kara insisted quietly, "If the virus spreads-"

"I'll die, I know, but it's a fate I'm willing to accept."

"No!" Kara planted herself in his path. "I am not gonna let you do this! I know you're upset about what's happening to you, but I'm not gonna let you go on some kamikaze mission!"

J'onn reached out and gripped her shoulders. "Kara, if I die, I want to die as myself, fighting for what I believe in. Not as some mutant horror show. Let me share the fate of my alien brothers and sisters, come what may."

Barry looked away, getting the feeling that he was witnessing something that was intensely personal and none of his business. He only turned back when he heard J'onn continuing to walk towards the exit, and followed him and Kara.

By the time they got to the port, two women who matched the file photos of Lena and Lillian Luthor were already there. The woman Barry recognised as Lena was standing in front of a briefcase computer with her hand on a switch. Beyond that was a huge rocket on a launcher, ready to fly off and kill hundreds of innocents. "Don't do it, Lena," Supergirl begged her friend.

"Why not?" Lena asked, her voice breaking just a bit, "I'm a Luthor." She twisted the switch, and the rocket blasted off into the sky.

"GO!" J'onn yelled, "We've got this!" Supergirl took off, and J'onn and Barry stepped forward. "You two are finished," he told the two women.

Lillian Luthor smirked. "You're wrong about that."

Only Barry's super-speed reflexes saved him from getting tackled by the cyborg from earlier – Hank Henshaw, Kara had said his name was – as he appeared pretty much out of nowhere. J'onn went flying and hit the ground so hard, he actually tore up the concrete.

Henshaw advanced on Barry, who easily evaded his punches. Then the speedster backed off and began to literally run circles around the cyborg. Once he'd built up enough energy, he slowed down just enough to hurl it all at Henshaw in the form of a lightning bolt.

Sadly, Barry seemed to keep coming up against enemies that could just shrug that attack off whenever he was on this Earth. Henshaw fired his eye laser at Barry, who ducked away with ease. He tried running at Henshaw and grabbing him – maybe he could throw him into the water and see how well the cyborg could float – but that turned out to be just as bad of an idea as trying to hit him, as Henshaw got a crushing grip on his arm and slammed him into the ground. Super-fast healing or not, that was going to hurt for a while.

J'onn got back into the game, trading punches with Henshaw and even knocking the metal cover off the side of his face, exposing the cybernetic components. It seemed to be going well for the Martian, until Henshaw slammed him against an electrical box. "You're a monster," Henshaw growled, "And I'm gonna send you back to Hell." He then threw J'onn into a shipping container, knocking it out from under the one stacked on top of it and bringing the top one down on J'onn.

"No!" Barry staggered to his feet and ran over.

To his surprise and relief, J'onn simply pushed the heavy metal container away and stood back up. "You're finally right, Henshaw," he said gravely, "I am a monster." He glanced over at Barry. "I've got this. Got get the Luthors."

Before Barry could argue, he suddenly morphed into a huge, snarling, green creature that was nearly twice as tall as the shipping container that had failed to crush him. Barry allowed himself to gape for a few seconds – and to relish the 'Holy crap, I'm in deep shit, now!' look on Henshaw's face.

Then he shook himself off and went after the two Luthor women. They'd run away during the fight, but it didn't take Barry long to find them, standing next to an expensive-looking black car parked nearby. Lillian had the briefcase computer and was about to hit a button, but Barry snatched it away before she had the chance.

"I don't think so," he taunted them, "Sorry, ladies, but that bio-weapon is not going off."

Lillian just smirked again. "Once again, you're wrong about that." She held up a small, flashing device. "I put in a failsafe. If this transmitter is more than ten feet away from the control module for five seconds…"

Even from high in the sky, the explosion could still be heard. Barry looked up and saw the fireball and the glowing orange ash cloud that spread out from it, expanding to cover the entire city. "No," he whispered, dropping the control module.

He looked over at J'onn, who was standing over a downed Henshaw, only to get blasted off his feet by the cyborg's laser eye. Henshaw stood up. "You might be an alien, but I'm Cyborg Superman!"

Then Supergirl came out of nowhere and slammed him into the ground, hard enough to apparently knock him out. "You may be a cyborg, but you are no Superman."

Barry wished they could call it a victory. But the Medusa Virus was still descending upon National City, and they had no way to stop it. If it had been covering a smaller area, Barry might have tried creating a wind funnel to divert it, but even he couldn't redirect that much.

J'onn got to his feet and gaze at the sky, shifting back into his human form. He closed his eyes, ready to accept his fate as the deadly ash slowly rained down on them. "I'm coming, M'yri'ah," he whispered.

But nothing happened. J'onn opened his eyes and looked back up to the sky in confusion.

"He should be dead," Lillian Luthor gasped, "All aliens should be dead." She turned to her adopted daughter, who was now wearing a very proud expression. "You. You switched out the isotope. You made the virus inert."

"I did," Lena admitted calmly as sirens began sounding, "I also called the police."

Barry shared a grin with Kara, who looked overjoyed; her friend had been on the side of the good guys, after all.

As the officers pulled up to arrest Lillian, Barry and Kara walked back over to J'onn. "You're okay!" Kara gasped.

"We all are," J'onn whispered, as though he was still trying to get used to the idea. They turned to secure Henshaw, only to see an empty crater in the concrete. Once again, the cyborg had obviously cut and run while they had been distracted.

"I hate it when they do that," Barry groaned.

Sunday, November 27th, 2016

It didn't take long for Eliza to come up with a cure, once the DEO got their hands on Cadmus's other samples of the virus. It also didn't take Mon-El very long to wake up once the cure was administered. He blinked up at all the people standing around his bed (Eliza, Kara, Barry, Alex, and Winn). "Am I dead?" he asked, "Is this Heaven?" His eyes flitted over to Barry. "And who are you?"

Eliza chuckled. "No, you're not dead. We were able to reverse-engineer a cure from a living sample of the virus."

"And when my mother says 'we'," Alex corrected, "she really means 'she'. But Winn, Barry, Cisco, and I watched enthusiastically."

"And I'm Barry Allen," Barry introduced himself, "Long story short, my friend Cisco and I came from a parallel universe to ask Kara for some help with a situation on my Earth, but you guys needed our help, first. Or not. Honestly, I think you would've been able to handle this just fine without us."

Kara patted him on the shoulder. "We're still grateful to you and Cisco for pitching in."

"It gets even better," Eliza said, "The Medusa Virus was so easily weaponized, I was able to turn it against a common enemy: J'onn's White Martian blood cells." Everyone turned and saw the green-skinned man standing there, looking far closer to human than he had been during the previous night's battle. Kara had explained to Barry the difference between the White and Green Martians, and why J'onn having a blood transfusion from a White Martian was causing him problems.

"J'onn!" Kara gasped, "You look great!"

J'onn grinned back at her. "I feel great. Thank you, Eliza." He shifted back to his human disguise as Eliza walked up and hugged him, which he gratefully returned.

"My pleasure," she told him warmly. Barry grinned. These people were just as much a family as he and the S.T.A.R. Labs crew were.

Cisco came into the room seconds later, having slipped out to go to the bathroom just before Mon-El woke up. "Oh, good, you're awake!" he said, grinning, "Does this mean we can go home, now?"

"I promise I'll be back soon," Kara assured her friends and family as she reached up to adjust the duffel bag strap that was slipping off her shoulder.

"Yeah, this alien invasion shouldn't take too long to deal with," Cisco commented behind her.

After Mon-El had woken up, Kara, Barry, Cisco, Winn, Eliza, and Alex had gone to Kara's apartment so that she could pack a bag with a few changes of clothing and other necessities before heading off to Earth-1.

"Are you sure you're okay with going alone?" James fretted. Winn had called him over so that James could at least say hello to Barry as well, as he'd been absent throughout this whole crisis.

"Yeah, it's fine. Besides, from what Cisco and Barry have told me, they've already got a mini-army gathered up, so it's not like it'll just be the three of us."

Alex stepped up and hugged her sister. "Come back safe," she whispered before turning to Barry, "If anything happens to my sister, I don't care how fast you can run or what Earth you're on; you won't be able to hide from me."

Barry nodded, a slightly scared expression on his face. "Maybe she's more like Sara than I thought," he murmured to Cisco.

Cisco snorted. "What, Lyla never scared the crap out of you?"

"No, but that could just be because I've never given her reason to do so."

"Not yet, anyway. She scares me."

"You accidentally taught Baby Sara a swear word; of course she was mad at you."

"How was I supposed to know the kid was right behind me?! I didn't even know she'd brought the little munchkin to S.T.A.R. Labs with her!"

"Guys!" Kara cried, interrupting their banter, "Are we going, or what?"

Both Barry and Cisco had the decency to look abashed. "Uh, right, yeah," Cisco muttered, "Let's get this show on the road!"

He slipped his Vibe Goggles on, and stuck his fist out into empty air. A swirling, watery blue portal formed around his hand, and he and Kara stood on either side of Barry. "You ready?" Barry asked a grinning Kara.

"Let's do this."

Barry grabbed his two travelling companions and sped into the breach, returning home to Earth-1 to face the alien invasion that threatened it.

THE END

Kara's comment about not knowing about the DEO base until July comes from the fact that 'Better Angels' and 'The Adventures of Supergirl' take place one right after the other. Since July 14th/15th is the midpoint between the airdates of those episodes (April 18th and October 10th), the last scene of 'Better Angels'/first scene of 'The Adventures of Supergirl' takes place on Jul 14th, 2016. By watching each episode and paying close attention to how much time passes, I was able to determine that the bulk of 'World's Finest' takes place just 2 days earlier, on Tuesday, July 12th. This means that the spacing between episodes is much greater than the spacing between their airdates.

My timeline is as follows:
1x01 'Pilot': Sat-Wed, Oct 24-28, 2015
1x02 'Stronger Together'-1x03 'Fight or Flight': Sun, Nov 1, 2015-Mon, Nov 9, 2015
1x04 'How Does She Do It?': Sun-Wed, Nov 15-18, 2015
1x05 'Livewire': Tues-Thurs, Nov 24-26, 2015 + Mon, Nov 30, 2015
1x06 'Red Faced': Tues-Fri, Dec 8-11, 2015
1x07 'Human for a Day'-1x09 'Blood Bonds': Sun, Dec 13, 2015-Thurs, Dec 17, 2015
1x10 'Childish Things': Mon-Tues, Jan 18-19, 2016
1x11 'Strange Visitor from Another Planet'-1x14 'Truth, Justice, and the American Way': Wed, Mar 16, 2016-Sun, Mar 27, 2016
1x15 'Solitude'-1x16 'Falling': Tues, May 31, 2016-Wed, Jun 8, 2016
1x17 'Manhunter'-2x03 'Welcome to Earth': Sun, Jul 10, 2016-Sun, Jul 24, 2016
2x04 'Survivors': Jul 2016
2x05 'Crossfire': Aug 2016?
2x06 'Changing': Sept 2016?
2x07 'The Darkest Place': Oct 2016?
2x08 'Medusa': Thurs-Mon, Nov 24-28, 2016
2x09 'Supergirl Lives': Thurs-Sat, Jan 5-7, 2017
2x10 'We Can Be Heroes': Tues-Fri, Jan 17-20, 2017
2x11 'The Martian Chronicles': Mon-Tues, Jan 30-31, 2017
2x12 'Luthors'-2x14 'Homecoming': Fri, Feb 10, 2017-Fri, Feb 17, 2017
2x15 'Exodus': Thurs-Sun, Mar 2-5, 2017
2x16 'Star-Crossed': Fri-Tues, Mar 17-21, 2017
2x17 'Distant Sun': Mon-Tues, Apr 3-4, 2017
2x18 'Ace Reporter': Thurs-Sun, Apr 27-30, 2017
2x19 'Alex': Mon-Tues, May 1-2, 2017
2x20 'City of Lost Children'-2x22 'Nevertheless She Persisted': Thurs, May 18, 2017-Tues, May 23, 2017

I don't yet have a finished timeline for 'Survivors', 'Crossfire', 'Changing', and 'The Darkest Place', mainly because 'Survivors' is the only episode of which I cannot seem to find a full version on YouTube (and no, Netflix is sadly not an option for me – I'd have a complete timeline by now if it was). The episodes that are grouped together in clumps are that way because so many episodes pick up right where the previous episode left off.

Oh, and Cisco hears the name J'onn J'onzz as 'John Jones', and never learns that J'onn is an alien, because otherwise that funny moment in 'Duet' where he finds out wouldn't get to happen.