It was really disappointing that Barry's visit to Earth-38 in the Flash part of the crossover was just reused footage from Supergirl. Tying in to the previous chapter, "Legacy," this scene serves as an alternative, showing what happened in that chapter from Caitlin's perspective.

As always, all characters belong to DC Comics and the CW, and this is written purely for fun. Thanks for reading. I appreciate it.

...

[Alternate scene, S.T.A.R. Labs hanger, replacing the clip of Barry and Cisco visiting National City (The Flash 3x08, "Invasion!")]

As Caitlin watched the telltale swirling vortex appear and disappear, signaling Barry's and Cisco's departure for Earth-38, she felt her brain going into meltdown, which was ironic considering her current personal problems.

Malevolent metahuman ice powers were threatening to take over her mind and personality, a quality the S.T.A.R. Labs team had yet to encounter, as evil metahumans tended to have questionable virtues prior to gaining abilities, not after. An outburst of hers during a manifestation of said evil powers had directly caused the rift between two of her best friends, and while Cisco deserved to know what Barry had done, she still felt guilty for the hostility between them. An alien invasion was threatening the very survival of humanity, a spaceship from the future had just materialized out of nowhere in the sky, and now Barry was going to recruit an alien from another dimension to fight on their side.

It almost made the idea of an evil speedster who traveled back in time to masquerade as a scientist seem normal.

Things didn't get much easier when she went outside the hanger with HR and Iris to meet the Legends crew. Although she was happy to see Ray, Jax, and Professor Stein again, and was pleased to meet Sara, Amaya, and Nate, she stopped dead in her tracks upon seeing Mick Rory. She didn't care what Barry said about Leonard Snart, at least, having a shred of honor in him somewhere. They were still responsible for kidnapping her and almost killing her in order to get to Barry a couple of years ago and for kidnapping Cisco and almost killing his brother just so he would build them new guns.

Rory seemed aware, at least, of the discomfort he was causing and kept his distance from her. Sara and Ray tried to explain that he had been through some experiences that had, somewhat, changed him, but Caitlin wasn't interested. It was only when they consented that Caitlin would hold the two of them directly responsible if Rory stepped out of line before she was satisfied, and she stalked away back to the computers inside the hanger, Iris and HR hurrying to keep up.

"Sooooooo," HR began, awkwardly attempting to break the tension. "What's the problem with the bald guy?"

"He's a notorious Central City criminal," Iris explained. "He actually usually rolls with a partner, Leonard Snart, and for some reason Barry thinks Snart is worth redeeming."

"Goes to show when Barry's wrong, he's really wrong."

Caitlin didn't need the glances from Iris and HR to know that came out harsher than she'd intended. Then again, her brain was melting down, so could she really be held responsible? After all…aliens.

"Okaaay," HR continued, again valiantly trying to continue the conversation. "So where's Snart?"

Iris shrugged. "No idea. It is a little weird; whenever they made the news they were practically inseparable."

"Fascinating," HR replied, tapping his chin with his miniature recording microphone, looking deep in thought. Suddenly, and somewhat alarmingly, his face split into a big grin. "I'm going to go interview him! This'll be great for my book!"

And with a twist on his heel, HR walked away.

Iris turned back to Caitlin, and Caitlin felt the need to apologize, given the many different ways Iris was close to Barry. "I'm sorry, Iris. I didn't mean to take a shot at Barry like that."

Iris shook her head. "Barry told me what happened to you and Cisco because of those creeps. I'd be mad, too."

Caitlin sighed and glanced to where HR was now passionately trying to coerce Rory into an interview, a request Rory showed precisely zero interest in granting. "I know everything pales in comparison to the threat of alien apocalypse, but—"

"Hey," Iris interrupted, putting her hand over Caitlin's. "Your feelings matter too, and they should have told us Rory was going to be here." She glanced back to the scene of HR sticking his microphone practically into Rory's mouth while asking rapid-fire questions, rolled her eyes, then turned her head back. "I'll talk to Barry when he gets back. Make sure he keeps watch over Rory along with Sara and Ray. And if that's not enough, I'll punch the bastard myself."

"Thanks, Iris," Caitlin smiled gratefully, squeezing her hand.

"Anytime," Iris smiled back. "Now, I'm going to go reel in HR before he gets himself killed."

"Good call," Caitlin replied, and Iris hurried off.

Caitlin sat back in her chair, feeling calmer after talking with Iris, and she was content to watch from a distance the various personalities of Star City, Central City, and the Waverider interact, but the peace was short-lived as an indicator lit up on the computer screen sitting in front of her. She clicked the flashing icon, and suddenly her screen was filled with an image of Cisco in an unfamiliar lab.

Wow, an impressed Caitlin thought, Cisco actually got the interdimensional communications to work. Cisco had briefed her before leaving that he might need to make a call, however, and she knew his time could be limited, so she kept it short.

"Hey Cisco."

"Hey Caitlin," Cisco smiled back, obviously pleased with his latest success.

A voice offscreen that Caitlin couldn't fully hear. Cisco turned his head away from Caitlin to answer it.

"Our Earth, yep," Cisco replied to the voice. "I fitted the gloves to include some limited communication functions."

Another voice. By now, Caitlin was getting curious.

"Cisco, what's going on? Do you need something?"

"Yeah, just one sec, Caitlin. Stand by to receive a biochem data transfer. I'll explain in a minute."

Biochemistry from another dimension? Caitlin thought excitedly. Yes, please.

…

This is insane, Caitlin thought several minutes later, pouring over diagrams and data on a virus designed by an alien race to kill other aliens. And I thought humans were xenophobic.

Cisco had quickly brought her up to speed on the situation and introduced her to both Eliza, that lab's apparent astrobiology expert, and Winn, their technical expert. (Or something along those lines.) Eliza got right to the point in explaining the details of the virus, enabling Caitlin to skip the basic questions and go right to the pointed inquiries that would help her evaluate this weapon. Despite the seriousness of the task, she couldn't help feeling some amusement glancing at Cisco and Winn, whose eyes glazed over as she and Eliza discussed the viral genome and pathogenic mechanism of the Kryptonian bio-agent.

That amusement was, of course, sadly short-lived as Caitlin shook her head. "I'm sorry, but I just can't support using this virus here on our Earth."

"These aliens are trying to kill us, Caitlin."

"Yes Cisco, I'm aware of that," she retorted sarcastically, "but Eliza's work looks sound to me, and what her research is saying is that the virus doesn't target aliens so much as it infects everyone and is simply ineffective in humans and Kryptonians."

"So?"

"So," Caitlin replied, "we happen to have at least two physiologies here on our Earth: human and metahuman."

Cisco winced. "Let me guess: our physiologies are different enough that the virus might think we're 'aliens' and kill us?"

"Bingo," Caitlin confirmed, "and metahuman diversity is as varied as the energies released when the particle accelerator exploded. There's no telling how any one metahuman will react to the virus."

"Crap," Cisco muttered. "Okay, thanks Caitlin. We will return to Plan A then."

"Recruit an alien and start punching?"

"Pretty much. What could go wrong?" With that, Cisco cut the connection.

Caitlin sat back. He's going to regret saying that out loud, she mused.