Crisis, 2019
"Ralph, you were supposed to be watching our six!" Nash yells, pulling Allegra away from a shadow demon and dissolving it with one precise shot. "We're getting swamped here!"
"Yeah, well, me too!" Ralph punches through three more of the demons, running back towards them.
"Where's Barry where we need him?" Hartley complains, blasting a demon apart without turning away from the quantum shield generator.
"Count yourselves lucky he's even alive. It was either both speedsters out of commission, or one dead," Frost says across the comms, firing icicles to discourage any stragglers from invading the cortex. "Handle yourselves without him. The horde is thinning out and the anti-matter readings are almost gone - we only need that shield for another hour or two."
One speedster dead.
Cisco realizes then, as he's monitoring Barry's vitals, that that was how the Flash was supposed to die. Sacrificing himself to kill the Anti-Monitor, to finish what Oliver Queen started. Harnessing all the speed force's power alone should have disintegrated him, dissolved him into ashes to never return.
Except it hadn't happened, because Barry hadn't been alone. Somewhere along the way, a different decision had been made, and the Crisis article no longer details Barry's death.
Although Barry's life might have been spared by the changed timeline, it might have cost another one.
Thawne's vitals are even weaker than Barry's - Caitlin doesn't think he will survive. His speed force is drained, healing factor gone.
The Velocity-X Cisco has stored in his lab crosses his mind. He ignores it. He shouldn't have to care about Thawne anymore.
A shadow demon's screech tears through the lab. It doesn't get far. The survivors are desperate to collapse the anti-matter shield now, picked off one by one by the exhausted but triumphant heroes. The fight is over. The Anti-Monitor is dead, and the wave that threatens this last Earth is dissipating.
A world has survived Crisis.
Barry's heart rate shoots up in an increased flurry of beeping. Cisco can't even turn around before he hears Barry gasp for air and sit up, eyes wide and confused.
"Barry's awake!" Cisco calls to Caitlin from across the lab.
"Bit busy," Frost hisses, freezing another demon before it can get to the pipeline. "Take over defending the lab for me, will you?"
Cisco plucks his goggles off the counter and tears another of the shadows apart with one precise vibrational wave. Frost's hair fades back to brown as she hurries past and into the lab.
"What happened?" Cisco hears Barry say.
"You survived Crisis."
Hartley Rathaway's voice comes through the intercom, accompanied with the dying shriek of another shadow. "It's not over yet."
. . .
Team Flash is in charge of keeping the shield generator that is defending Earth-Prime from anti-matter intact. Allegra defends Nash and Hartley, who are keeping it running. Once Barry is back on his feet, he joins Ralph in the pipeline to help keep the wave of incoming shadow demons at bay. They've created a funnel with the accelerator, and the weakened demons are easy targets.
Even Iris is blasting away, each shot dismantling demons with unsettling accuracy. Barry's speed is laughable- it's a wonder he's even generating lightning at all-but it's enough to phase. Cisco has his powers back and Frost is throwing icicles.
The lab is the perfect place to launch the shield, infrastructure and all. Cisco wonders, briefly, if Thawne built it with the idea in mind. It's far-fetched foresight, but future knowledge has a tendency to do that.
The rest of the Crisis heroes who are still strong enough to fight are dispersed throughout Central City, saving civilians from the rest of the horde. The Kryptonians and Luthor are up the air as Team Arrow is down in the streets, tearing the rest of the Anti-Monitor's forces apart.
The fighting doesn't end until that evening, when a full city search reveals no trace of anti-matter or shadow demons. Even so, they decide to keep the shield up for a few more days.
They mourn Oliver. They mourn the meta-humans that fell saving the city. But in the end, everyone else goes home alive.
Team Flash is intact, alive, celebrating-albeit with a problem.
Thawne is dying.
He hasn't woken up yet, and he might never.
Hartley, who is planning on sticking around, isn't bothered. He always wanted revenge for what Dr. Wells did. Cisco won't say a word, Caitlin is having reservations about not doing anything, and Barry, surprisingly, wants to find a way to save him.
"You don't understand. He's the reason why I survived Crisis. It's because of me that he's dying."
"Even so, there's nothing we can do," Cisco snaps. That is a lie. He knows exactly how to save Thawne - he just doesn't want to. Maybe that makes him selfish, but he's not like Barry.
Still, the notion doesn't leave him. Thawne had saved Barry's life expecting to die. Whatever reason led him to have a change of heart -
Cisco can't do it. He can't save Thawne.
. . .
Cisco is still last to leave the lab.
The changes to the physics of Earth-Prime fascinate him to no end-so many recalculations have to be done that he doesn't see how to make them all, to catalog all the effects, to understand.
He is the only one to hear Thawne die.
It is subtle, at first. He is in the cortex when it gets too quiet, when he realizes the insistent beeping from Caitlin's lab is gone. Even then he walks in a disillusioned trance to see the readings gone dead, to see no pulse detected from the monitors.
The panic hits him all at once. He's dead.
I killed him.
He's already running to his lab when he fully understands that he can't have that weighing his mind.
It's selfish. But Cisco saves him. He gets the Velocity-X, administers it, watches Thawne's powers return. He doesn't wake up, and Cisco is listening to the steady beep when Barry skids to a hasty stop.
"His speed force died," he says urgently, looking past Cisco and into Caitlin's lab. "What happened? What did you do?"
He connects the dots when Cisco lets the empty vial fall from his hand.
"You saved him?"
Cisco hasn't processed his own decision, and his voice sounds distant to his own ears. "Velocity-X. I used it... to try to save you from Bloodwork."
"You..." Barry looks back from Thawne to the Velocity-X. "You always knew how to save him."
"I was going to let him die," Cisco's voice cracks. "I was going to kill him in cold blood and I would've done it. I..."
He expects Barry to be appalled. To maintain that, "they don't kill". That as heroes, they do the right thing immediately.
To which Cisco might have replied, "Maybe I'm not a hero, then."
Instead, Barry says gently, "That was brave of you."
"Is it?" Cisco mutters. "You would never have struggled with this."
"I came close to killing him in the Crisis of Earth-X, you know." Barry sits down in the cortex, a thoughtful look on his face as he spins slowly in his chair. "Phased my hand right over his heart as he yelled at me to kill him. I couldn't do it."
"Killing someone is very different than letting them die."
"And we both came close. But I was going to do it out of anger, and anger is the worst thing of all. I learned to let it go when I was in the Vanishing Point. But you didn't do it out of anger, did you?"
Cisco realizes he doesn't know.
Finally, he says. "Out of fear."
Barry smiles. "But not for your own life."
"No," Cisco admits. "I'm scared... he's going to kill someone else I care about, and I won't have anyone to blame but myself." The panic returns, and he's back to fearing what he's done. "How many people have I condemned by saving him?"
"We can try to make it none. And if we fail, then that's his fault, not ours."
"You really think he can change?" Cisco asks abruptly. "After he killed your mother, your daughter, me?"
"Nora asked me that, once." Barry shakes his head ruefully. "Asked me if I thought anyone could change, soon after I told her how my mother died. I should have connected the dots then about who she was working with, because she asked about Eobard."
"What did you tell her?"
"Yes," Barry says simply. "I told her I really believed he could change. He already has." He gestures to Caitlin's lab, to where Thawne is lying unconscious. "Or else I wouldn't be here to have this conversation. I would have died in Crisis, you would be leading the team, and there would be two funerals to attend."
Cisco falls silent, takes a deep breath. Looks at Thawne again, who's breathing steadily, who will wake up soon. And he knows he's changed some unwritten timeline, averted some unwritten future.
Both the Flash and his reverse have survived, where one should have died. But Cisco understands that he can't take responsibility for the unpredictable, for whatever happens next. And so he nods, comes to term with his decision, and follows Barry out of the cortex.
Midnight hits the clock, and Crisis is over.