Author's Notes: "Erudio" is Latin for instruct, teach, educate, train, enlighten, smooth.

It takes Caitlin and Cisco forty-five minutes to find him.

Barry kneels on the edge of the cliff, listening to the muted thunder of the falls and the more distant rumble of a true storm approaching from the south. Soon rain will drench the area and swell the falls to an even greater deluge, but it's inconsequential. What once might have driven him to stay dry is no more obtrusive than a cool breeze, compelling but not dictatorial. Lightning can handle wind and rain, and thunder cannot touch him.

Cisco says his name. Barry doesn't respond, close enough to the edge that neither of them approach. He won't jump – the thought almost makes him laugh, a horrible, unhappy sound because you can't jump – but they don't know. So they keep their distance, at an impasse, until at last the rain comes.

Then Cisco puts a hand on his shoulder and says, "Barry."

Barry swallows a retort and pushes himself to his feet. Cisco backs away, feeling the electric current surging under his skin. Barry doesn't wrestle it back to a manageable level; the lightning is easier to feel than the profound sense of loss. At least it keeps him safe, has meaning, is something.

A deep breath steadies his trembling legs; a slower exhale steadies his mind. Planting his feet in the grassy turf, he spares Caitlin and Cisco a momentary glance before turning towards the open space in front of him and taking off.

He beats them to Star Labs by twenty minutes, breaking into Dr. Wells' time capsule and sinking against a wall. He bites down on his fist hard enough that he thinks he might break the skin of the suit, but its integrity holds. With his back to the world and a mounting sense of despair rising in his throat, he groans, a low, unceasing sound as sure as the thunder outside his world.

He didn't deserve to live for them.

Ronnie and Eddie, Cisco and Joe? He was their undoing, the point of impact which buckled the courses of their lives, shortening a triumphal arc into a catastrophic crash, smashing into an end far sooner than anticipated. The first shockwave took out dozens of casualties, people whose lives would never be the same, dousing them in radiation, stagnating their existence from forty years to forty weeks (Clyde Mardon). The second shockwave was close on its heels, threatening to destroy Central City just when it seemed things would finally be okay: metahuman attacks, the dead and wounded mere collateral in the game of superhumans.

The third, fourth, and fifth shock waves were close together, coming in ripples of less violent origin but equal intensity:

You killed my mother.

Harrison Wells is the Reverse Flash.

I know how we can stop him.

The sixth wave broke, the seventh and eighth tripping over themselves as they diffused.

Six: I can save Mom.

Seven: for a moment, an arresting clarity, as if a second consciousness entered his mind, pinning down rational thought and ordering, Don't do it.

Eight: I'm sorry.

I'm starting to think "Joe I'm Sorry" is my actual name, given how often you say it to me.

The return to his own reality was the fracture point, where noble aspirations crumbled in the face of the insurmountable strength of his opponent. Sobriety gave Barry clarity, but rage gave Eobard strength. Eobard's anger punched through Barry with every fist that made contact, as surely as bone and flesh, digging into the brick and mortar of who he was. The encounter was a fatal reminder that Barry was not the god of his own universe, destined to choose his own path, but borne along by the shockwaves he created, neither able to stop nor alter their momentum.

When the Reverse Flash put him up against the wall, Barry knew it with absolute certainty: I am about to die.

Then a gunshot rang out and the pain in his shoulder never-was.

Each wave came faster than the last: Eddie's dead, we-closed-the wormhole-this-can't-be-happening, it-cannot-be-stopped, I-have-to-try, I-can't-keep-this-up-much-longer, Ronnie NO.

Barry's ears rang, his chest hurt, and the weight of knowing he opened the singularity bore down on him until Barry could barely breathe. He didn't deserve to be in their company. He didn't deserve to be alive. The thought of justifying his own existence to them strangled him until he wanted to run back in time just so he could die instead, so he could stop all of this from happening, all of it.

But that wasn't his first priority. His first priority was Central City. Guilt had to wait.

He Flashed through the city well into the night, working against the tide of misery threatening to engulf it. He kick-started hospital generators and jump-started ambulances, fetched gear for firefighters and helped them douse fires, coordinated with police to maximize the efficiency of rescues and verified the true emptiness of a building before it came down no-matter-what. He worked until his bones ached to reunite families and prevent the death toll from climbing any higher, ferrying no less than eighty kids from after-school activities to their parents, monitoring the streets for any opportunistic criminals and stopping three robberies before the would-be robbers finished pocketing their first prize, depositing them ungently at the feet of the nearest officer.

When he collapsed on Star Labs' doorstep eight hours later, Cisco caught him, hauling him inside before anyone could capture The Flash and unveil him to an eager crowd of reporters. Even in the midst of catastrophe, Barry couldn't put it past them; his own curiosity regarding the Arrow had been insatiable, he could only imagine what it was like to know there was a person who could run faster than the speed of sound in their midst. It would be a delight, but it would also be the end of Barry's life, faster than any unforeseen bullet or too-strong metahuman.

Cisco got him to safety. Brought him down to the particle accelerator. Left him alone.

Breathing slowly through his mouth, eyes closed, Barry leans his head back against the oversized braille wall and wonders why he can endure pain on an unprecedented scale but can't bring himself to go back and end his torment. He has been the Flash for almost two years, saving dozens of lives (which wouldn't have needed saving if it weren't for you). He has had the lightning under his skin longer than any person has the right to, a gift beyond words, beyond comparison. He has made friends and shared some of the highlights of his life with them. He has done the impossible (nothing is truly impossible).

He has lived a full life.

It's time to pay up.

It would be quick. And the repercussions would change their world – the Pandora's box would stay closed, the particle accelerator explosion would never happen, and the countless lives directly impacted by their actions would stay on their original trajectory. Eddie would still be alive; Iris and he would be engaged. Dr. Harrison Wells – a man you never knew – would be the one standing at the podium announcing to an enraptured crowd that the future had arrived, carrying a scientific legacy that would change the course of history. Ronnie would still be alive. Even Caitlin and Cisco would benefit directly: without the anathema associated with Star Labs, their futures would advance more quickly in the field.

And all you have to do is die.

Barry opens his eyes, looking around the room, aware of his shaking hands.

This has gone too far. Pushing himself to his feet, he walks up to that solitary podium. You can't stop Zoom. You can't even stop Trajectory.

(Trajectory is dead.)

Barry puts a hand on the sphere. You have to end it.

"Gideon."

A mechanical, almost sweet voice responds, "Good evening, Barry Allen."

Barry exhales slowly, feeling the weakness in his own legs, the heaviness in his chest. "Why did I create you?" he asks.

"To teach."

It isn't the answer he's expecting; Barry's brow furrows. "I don't understand."

Gideon draws up a screen, hundreds of articles at his disposal – thousands, even. "To teach," Gideon repeats calmly. Pulling up one of the folders, Gideon sifts rapidly through the articles, calling up a document entitled, 92: Fusion.

It's an answer to the energy crisis.

At thirteen hundred digital pages, it's a dense read, but Barry sifts through it in record time, aware of the cramping in his muscles only when he straightens his back, five minutes later, and exhales. He goes back and rereads it, trying to comprehend this light-years-ahead-of-CERN knowledge, surrendered freely from the future.

Then Gideon calls up a new document entitled 93: Amendments to 92: Fusion and Barry devours it, too, ignoring the pulsing pain behind his eyes from strain because it's important, and the amendments make sense, the entire theory makes sense, and they've achieved it but they have not been able to use it but this – this could be the answer to everything.

This is everything humankind has ever learned up to this point.

Does that include twerking?

That is what the particle accelerator can teach us. It will literally change everything.

Gideon says, "In one thousand, eight hundred, and ninety-two years, you log 8,963 entries."

Barry blinks. Says slowly: "That's not possible."

Gideon materializes in AI form, actually smiling at him. "Anything is possible, Mr. Allen." Then, letting the database take over the screen, Gideon adds, "Most of these records are preserved in the future. You created me to protect them. To be your voice to distant generations. To teach."

2451: Genetic Therapy, Osteoporosis and 6837: Genetic Therapy, Melanoma stand out as Gideon sifts through more articles. Medical Advancements alone claim 4,200 articles, Nuclear Energy weighs in at 2,500, Advancements in Technology claim 1,000, and Miscellaneous captures 800.

The remaining 400 articles belong to something called Speed.

Intermittently, the title reappears in stacks: 62-68: Speedsters, 200-298: Speed Force, 3150-4200: Uses of Speed. Early entries denotes 3-8: Dangers of Speed.

The hard-won knowledge of hundreds of generations is before him. Barry cannot speak, overwhelmed. Caught off-guard.

Then Gideon disperses the scientific articles, calling up 63 single-page entries.

The first is dated nearly five years from now, 2021.

Oct 1, 2021

Success! I can't believe it. Wally owes me a beer; right on time!

The world's first Genetic Investigation Database and Energy Optimization Network (GIDEON) will challenge what it means to be human in the 21st century. Dr. Wells didn't leave me a legacy; he gave me a mission. The future changes, but the steps humankind takes can't be erased. I intend to follow those trails and learn from them to better my world.

I have this gift; it's time to use it for something that won't die with me.

GIDEON is the answer: a cumulative record of libraries of Alexandria from the future. These ideas are in danger: in their timelines, they're in danger of being destroyed. Painful interludes of trial and error will mean millions die in the search for something that should have been theirs. The Genetic Investigation Database will preserve the medical advancements of the future; the Energy Optimization Network will compile ideas to broaden our current understanding of physics.

The future is here – and GIDEON is the response to that future.

Gotta run – but GIDEON! We did it!

Eight entries later, Barry has to pause again, zeroing in on an article written almost three months later.

January, 4 2022

The future scares me, GIDEON.

Not because of tsunamis or metahumans or world-ending apocalypses. They deserve attention, but they don't keep me up at night. I know that I'm going to die someday; making peace with that idea is what kept me alive this long.

Sitting here, talking to you now, I know that this is something I've wanted, but it still scares me. Being a dad is a big responsibility. There's no instruction book (and trust me, I've looked). Sometimes it seems like it's been centuries since Iris and I had that first conversation – and in a way, it has; you won't believe how cute the great-grandkids are, GIDEON – but in reality, it's only been a few months. And I know I want it – she wants it, too.

But what if I'm not ready?

I know it's going to work out okay. But that's just one timeline. There are thousands, and what keeps me up at night – which truly scares me – is that I can't control which timeline my life follows.

A lot of them are great. I have kids who win Nobel prizes. I have kids who sing, who dance, who play-wright, who dig up history. I have autistic kids, kids who love animals, kids who loves books, kids who love creating things. I have athletic kids, intelligent, funny, beautiful, wonderful kids.

Whenever I see them, GIDEON, I want to take them home with me. It's like they're already mine – even though they haven't been born yet. I want them to know how proud I am that they exist, how lucky Iris and I are to have them.

But in too many universes, I bury my kids. I watch them wither away. I watch inexplicable accidents take them. I watch them become criminals. I watch our relationship fracture and never repair itself, dying without being a father.

I can't know which trajectory I'm on, what the impact is. Whether it's the ice cream Iris and I eat, or the amount of paperwork I complete in a week, or which strangers I save. I don't know how to reconcile my decisions with the future, to pay-it-forward. I want to do the right thing.

Is it too soon? I don't know.

But the future scares me, GIDEON.

Exhaling sharply, Barry leans against the podium, tempted to shut the entire system down and burn it, overwhelmed with an unspeakable emotion. He isn't reading someone else's words: he's living them, aware in the same acute way of that Barry's distress, how he pauses between sentences, how he trembles with excitement and anxiety, how he wants but also dreads.

Fifteen entries pass innocuously, documenting future Barry's travels – King Shark has kids and they are not friendly, I met another doppelganger, I need to wear a spacesuit because the lack of oxygen in that last universe almost killed me – and then the twenty-fifth entry captures his attention.

March 22, 2022

Babies.

I should say something more, but it's three thirty-six AM, Iris is asleep, and in each arm I have one of my kids.

I should be scared, GIDEON, but honestly, it feels like I've been waiting for this day for centuries.

They're absolutely perfect.

Things take a slightly cooler tone by the end of the year, Barry skimming through entries, oddly choked-up, afraid to ruin his own future by spoiling that uncertainty.

It won't be the same now, he reminds himself, pausing Gideon at the fifty-second entry.

December 8, 2023

I'm thirty-four years old, but I met a speedster from the thirty-eighth century yesterday and I can't shake the feeling that I'm as old as he is, centuries older than I should be.

I get tired too often. My runs are jogs; my mind slips in the wrong places; my appetite is vanishingly low.

Iris says I need to rest, that it's related to overwork. All I have to do is take some time off until I feel better.

The future is starting to scare me again, GIDEON.

Two entries later:

February 18, 2024

I couldn't get out of bed today.

Something is wrong, GIDEON.

Sixty.

March 4, 2024

The sun is shining in Mudville, GIDEON.

Iris was right: bedrest did the trick. My relief knows no bounds; the lightning is impatient. It wants to run again.

I need to take it slow, but it feels good to be back.

Sixty-one.

March 27, 2024

We've logged almost 9,000 articles, GIDEON.

It still catches me off guard at times. Of course, most of those are copy-pasted from the future: perks of having a stellar short-term memory. They aren't verbatim – and it's possible I missed the most important points, that the knowledge will turn out to be void when something bigger and better comes along – but they're a foundation.

Insurance.

I'm not a writer, but I am a scientist, and the long-term effect is the same.

You are my insurance, GIDEON. To teach the future, when the right time comes.

Sixty-two.

April 16, 2024

I twisted my ankle and it took almost twelve hours to heal.

The wear and tear of my job is intense, GIDEON, but I can't help worrying about that.

Am I aging faster? If so, can I stop it?

I want to be here for them, GIDEON.

And at last, sixty-three.

April 25, 2024

I kissed Iris this morning and it felt like goodbye.

The lightning knows something, GIDEON, which is why I feel compelled to talk to you now instead of later.

For some reason, I don't think there will be a 'later.'

It could be nothing. I've had false alarms before, envisioning an end that only comes in a divergent timeline. They fade over time, but they're intensely real in the moment. I can almost see the Black Flash looming over my shoulder.

This morning, we drank coffee together. It just sat there, quietly, while I finished my drink. It's a disarming sensation, even though I know It is a hallucination. By tomorrow, It will be gone again.

It's probably nothing.

But you are my insurance, GIDEON. So I have to say it.

This program has been a success. We have logged enough entries to ground the work of thousands of future scientists. Publication of the GIDEON system will fall into the hands of my family; I have encoded a message for her titled: One Favor. It will explain everything.

Our journey does not end here, GIDEON. I have seen the future, and no matter what happens today, a thousand Barry's live on, raising my kids.

I didn't know what I was getting into when I picked up that red suit ten years ago, GIDEON. A lot of people died because I wasn't fast enough or strong enough or smart enough to save them.

But on other Earths, I was. On other Earths, I had my friends, my family, Team Arrow on my side. Those people don't die in every timeline; their lives continue in the multiverse, ensured a billion times over.

My work has not been to make the provocative claims that will alter our history. It's been to compile a list of those people who have devoted their lives to work which can enrich the futures of countless others.

I want other Flashes to live, GIDEON. I want other Irises, other Joes, other Wally's and Jesse's to live. I want the multiverse to thrive, even if I am not there to see it.

I've had a good life, GIDEON. I hope it doesn't end here.

Until next time,

Barry West-Allen

There are no more entries.

Barry reaches up to press both hands against his eyes.

April 25, 2024.

It's a date emblazoned in his mind ever since he first saw the newspaper article: Flash Vanishes in Crisis.

Barry didn't just disappear that day.

He died that day.

Looking at the full breadth of his life work, he can't help but marvel at how much he did in thirty-five years.

Sixty-three personal entries and thousands of scientific articles, each primed for the public. Clinical trials will still take decades, and the machinery for many of the more futuristic technology won't be viable without large sums of money and patience, but it's here.

"Did Eobard Thawne ever see those entries?" he asks, slow, rasping.

Gideon pulls up a completely different screen, meticulously organized – down to videos and Barry's throat tightens because Eddie and Ronnie are there – and noticeably scarcer. All she says is, "Professor Thawne did not have authorization to access the archives."

Barry blinks. Shaking his head as though to dispel an errant thought, he adds, "I don't understand."

"Only BARRY ALLEN, IRIS WEST, WALLY WEST, and JOE WEST have permission to unlock the archives," Gideon explains, flashing each name on the screen as she does so. "All other users must be coded in by BARRY ALLEN to have access."

He never knew about these.

Barry urges quietly, "Gideon, pull up the Speed files."

"Certainly."

Gideon obliges, and a quick perusal of the first entry almost knocks him off his feet.

It's all here.

The explanations are scarcer than he would like, but the basic points they hit upon makes sense to him.

Speed is unstable. Used for extended periods of time, it can: rupture timelines, disrupt the Speed Force, and annihilate speedsters.

Barry whistles low. Trajectory.

Speed is replicable, but artificial speed is dangerous. Artificial speed is: highly addictive, molecularly unstable, and unable to sustain speedsters. Time travel is not possible with artificial speed.

Something – clicks.

Time travel is not possible with artificial speed.

Eobard Thawne used tachyons to boost his speed, making him faster than the Flash, and yet – he hadn't been able to travel back to his own time on his own.

There's an entire treasure chest of Speed-related knowledge to explore, and Barry wants to, but there's a deluge of exhaustion and something approaching satisfaction sinking into him.

It wasn't in vain.

Clearing his throat, he asks quietly, "Pull up a new personal entry, Gideon."

"Certainly."

The blank screen looks back at him, expectant, and he can almost see another Barry standing there, arms folded, waiting patiently.

March 22, 2016

I have a new mission.

I need to stay alive for them. I need to fulfill something.

I need to be a part of the future.

. o .

The air is heady, the sun is bright and light and low on the horizon, and the sleepy city scarcely stirs as Barry picks up a stack of coffees at Jitters. He loves the way pocket change clicks around the tip jar, the way coffee smells before the first taste, the way freshly scrubbed tables invite him to grab his laptop and a seat and bask for a while. He should feel tired – and he is – but mostly he feels very alive.

The lightning under his skin feels strong, powerful, ready-for-anything.

Walking back to Star Labs (running cools the coffees; a lesson he learned the hard way), he thinks, Zoom has to be stopped.

It isn't a question of if; it's when.

For some reason, the idea that he's already visited the future – deep into the future, thousands of years, even – calms him. He's faced worse things than Zoom; he's faced much more powerful beings than himself. And he's come home each time, adding something to his own universe as he seeks to understand those universes around him.

He's come home because home is his future, something to look forward to, coffee and hugs and karaoke, routines and adventures and gifts, surprises and spectacular new finds.

But most of all, Barry comes home because Caitlin and Cisco are waiting for him. Their relieved and almost apologetic expressions compel him to set the coffees aside and hug them, savoring the opportunity to do so.

You get to have another day.

Enjoy it.

"I'm sorry," he tells them, hugging them hard without hurting them. "I shouldn't have run off."

"We're just glad to have you back," Cisco says, hugging him back.

"We're gonna work it out," Caitlin adds softly.

Barry nods, releasing them slowly.

Something stabilizes between them, an unspoken promise to face the future – whatever it holds – together.

And Barry realizes that as much as he needs them – how much he has to stay alive for them – that they need him, too.

I'll take care of them, he promises the future.

Speaking of the future, Barry picks up a cup of coffee and says, "I think I know how to stop Zoom."

Caitlin arches both eyebrows. Cisco says, "Really?"

There's a moment when Barry thinks about showing them Gideon's database, settling on relevant information for now. One step at a time.

Zoom first.

You get to have another day.

Use it.

. o .

When Barry has a moment between strategizing on the marker board and fetching lunch, he stops by the time vault.

Pulling up the system, he greets, "Gideon."

"Greetings, Barry Allen."

"I'm granting full authorization to CAITLIN SNOW and CISCO RAMON."

Gideon AI's counterpart actually smiles. "Certainly," Gideon replies, pulling up the list and adding their names.

You get to have another day.

Insure it.

. o .

On April 26, 2024, Barry calls up Gideon's program.

Smiling, he leans his hands against the podium. Thinks about the family he has, the friends he has, the science he can use. He savors the lightning working in tandem with him under his skin, monitored, kept in check (Speed is unstable) to prevent the inevitable catastrophe, a disintegration of the Speed Force, an undoing of his own being.

It wasn't easy, and it's still a new science – the future Barry never explored the limits and risks associated with Speed – but they did it.

They made it to April 26, 2024.

In a cheerful, unhindered voice, Barry says, "Uncharted territory, Gideon."

Gideon smiles back and replies calmly, "It always has been."

Pulling up a new entry, Barry rocks back on his heels, feeling the momentousness of the occasion.

All he says is, "We get to have another day."