The storm over Manhattan beat against the glass ribs of Stark Industries.
Thunder rolled between skyscrapers. Rain hammered the windows hard enough to make them tremble, while somewhere beneath the building, one of Howard Stark's experimental reactors hummed steadily through the night.
Howard barely noticed any of it.
He had been pacing the same stretch of sterile white floor for the better part of twenty minutes.
Back.
Forth.
Back.
Forth.
Maria Stark finally tightened her hand around his hard enough to make him wince.
"You keep pacing like that," she said between breaths, "and you're going to wear a hole straight through the floor."
Howard looked down at their joined hands.
"Pacing keeps the mind sharp."
Maria stared at him.
Even exhausted and in labour, she somehow managed to give him the exact look that had ended arguments throughout their marriage.
"Then sharpen it somewhere else."
Howard opened his mouth.
Thought better of it.
Edward Jarvis stood near the back wall, maintaining the dignified expression expected of the Stark family's butler.
The tiny twitch at the corner of his mouth betrayed him.
Howard pointed at him.
"Not a word."
"I said nothing, sir."
"You were thinking something."
"I cannot imagine what you mean."
Then—
Every monitor in the room screamed.
Howard spun around.
The steady lines tracking Maria and the baby suddenly distorted. Numbers jumped wildly across the screens.
One monitor went black.
Then another.
Then another.
The attending doctor leaned over the equipment.
"What happened?"
A nurse checked the connections.
"They're still connected."
"Reset them."
"I already did."
Howard stopped moving.
That frightened him more than the alarms.
The doctor stared at the fetal monitor.
His expression changed.
"Heart trace is gone."
Howard's stomach dropped.
"What?"
Maria immediately tried to sit upright.
"What does that mean?"
"Mrs. Stark, please—"
"What does that mean?"
The doctor looked between the monitors.
"I can't find your son's heartbeat."
Howard was beside him instantly.
"Then find it."
"Mr. Stark—"
"You have half a billion dollars' worth of medical technology in this building. Find my son's heartbeat."
The doctor swallowed.
Then something strange happened.
A new rhythm appeared on every monitor simultaneously.
Not a heartbeat.
A pulse.
Perfectly spaced.
Perfectly consistent.
And accompanied by an energy reading that shouldn't have existed inside a human body.
Howard stared.
"What the hell is that?"
The lights flickered.
Once.
Twice.
Then lightning illuminated the room—
—and beneath Maria's skin, for just a moment, Howard saw blue light.
Maria saw his face.
"Howard?"
He couldn't answer.
Another contraction hit.
Everything happened quickly after that.
Doctors moved.
Nurses shouted.
Howard forgot about the machines and held Maria's hand.
And then—
A baby cried.
For one beautiful second, that was the only thing Howard heard.
His son was alive.
Then he noticed the other sound.
Hmmmmmmmm.
Soft.
Almost soothing.
Howard slowly looked toward the newborn.
The doctor had frozen.
So had the nurses.
The infant looked completely human.
Tiny hands.
Dark hair.
Red, angry face announcing his displeasure with being born.
But underneath his chest was a faint blue glow.
Not sitting underneath the skin like an implanted machine.
Deeper.
Integrated.
Every few moments, the light gently intensified.
Hmmmmmmmm.
Maria immediately reached out.
"Give him to me."
The doctor hesitated.
"Now."
That ended the discussion.
They placed Anthony Edward Stark into his mother's arms.
The crying slowly stopped.
Maria looked down at him.
Tony opened his eyes.
The blue light beneath his chest pulsed.
Maria smiled.
"He's beautiful."
Howard couldn't move.
His scientific mind was screaming at him.
Energy readings.
Biological impossibilities.
Quirk mutations.
Cellular integration.
The faint electromagnetic field Tony was already producing.
But underneath all of that was something much simpler.
Fear.
Howard Stark could solve problems.
He could build weapons.
He could build reactors.
He could take machines apart and understand exactly why they worked.
But this was his son.
And Howard had absolutely no idea what he was looking at.
"He has a reactor inside him."
The doctor slowly shook his head.
"I don't think 'inside' is the right word."
Howard looked at him.
The doctor brought up the scans.
Blood vessels surrounded the structure.
Nerves connected directly into it.
Cardiac tissue intertwined with an organic interface around the reactor, with Tony's natural heart and the strange organ working together as a single cardiovascular system.
It hadn't been implanted.
It had grown with him.
The reactor wasn't replacing Tony's heart.
It was part of the same system.
An organ no human being had ever possessed before.
Howard whispered, "Jesus."
Maria didn't care about any of that yet.
She touched Tony's cheek.
"He's breathing."
Howard looked at her.
"He's alive."
"Then everything else can wait."
From the back of the room, Jarvis finally approached.
He looked at the newborn Stark.
The baby looked back.
Jarvis bowed his head slightly.
"Welcome, young Master Stark."
Tony's reactor hummed.
Jarvis raised an eyebrow.
Howard actually laughed.
"I think he likes you."
"I shall consider that my first successful negotiation with him, sir."
Maria laughed tiredly.
"He hums."
Howard looked at his son again.
The fear was still there.
But now something else had joined it.
Wonder.
"Then I suppose," Howard murmured, "the world just found a new note."
By four years old, Tony's hum had become background noise in the Stark household.
Maria barely noticed it anymore.
Jarvis claimed he could tell Tony's mood from the pitch.
Howard denied doing exactly the same thing.
Excited Tony hummed faster.
Sleeping Tony produced a low, almost inaudible vibration.
Angry Tony made nearby electronics flicker.
And curious Tony—
which unfortunately was Tony approximately ninety percent of the time—
made everything interesting.
Dr. Evelyn Ross moved a scanner across his chest.
Tony lay on the examination table staring at the holographic image above him.
His cardiovascular system appeared first.
Then his nervous system.
Then the Arc Reactor.
And finally thousands upon thousands of tiny pathways spreading throughout his body.
Ross enlarged the image.
Howard leaned closer.
Maria watched both scientists instead of the hologram.
That was how she knew something was unusual.
Howard stopped talking.
Howard Stark never stopped talking when he understood something.
"Howard?"
He zoomed further in.
Tony's blood looked perfectly normal to the naked eye.
Under advanced imaging, it wasn't.
The reactor's energy was being distributed throughout his bloodstream by microscopic biological structures created by Tony's Quirk factor. His cells weren't being burned by the energy.
They were using it.
Ross stared at the results.
"His blood is functioning as an energy-distribution medium."
Howard's eyes narrowed.
"Like wiring."
"Better than wiring."
She switched scans.
"His nervous system is doing the same thing. Every year the integration becomes more sophisticated."
Maria immediately asked the only question she cared about.
"Is it hurting him?"
Ross smiled.
"No."
Tony raised his hand.
Everyone looked at him.
"So I'm not dying?"
Maria's expression immediately softened.
"No, sweetheart."
"Good."
Tony looked back at the hologram.
"Because dying sounds boring."
Howard snorted.
Maria gave him a look.
"Don't encourage him."
"I didn't say anything."
"You laughed."
Tony pointed toward the scan.
"So what's my Quirk?"
Ross glanced toward Howard.
Howard looked at his son.
"That's complicated."
Tony frowned.
"Why?"
"Because most Quirks let someone do something."
Howard tapped the hologram.
"Yours changed what you are."
Tony's eyes widened.
"Cool."
Of course that was his reaction.
Ross began entering the official classification.
"Integrated bio-technological mutation. Cardiovascular energy generation. Accelerated cellular repair. Enhanced neurological processing. Electromagnetic technological interfacing…"
Howard looked over.
"That's going to be one hell of a Quirk registration form."
Ross smiled.
"Fortunately, I've already picked a name."
Tony sat upright.
"What?"
She entered it.
QUIRK: EXTREMIS
Howard raised an eyebrow.
"Extremis?"
"Latin. The farthest point. The extreme."
She looked at Tony.
"Because medically speaking, we don't know where his Quirk ends."
Tony considered that.
Then grinned.
"I like it."
Howard built Tony's first regulator that night.
Not because the Arc Reactor was unstable.
That was something Howard made very clear.
The reactor was probably the most stable thing he'd ever studied.
Tony was the unstable part.
Specifically, Tony's four-year-old emotional control.
The bracelet wrapped comfortably around his wrist.
Tony stared at it.
"What does it do?"
"Stops you accidentally turning the toaster on when you're excited."
Tony blinked.
"I did that?"
"Three times."
"I wasn't touching it."
"Exactly."
Tony's grin slowly appeared.
Howard immediately pointed at him.
"No."
"I didn't say anything."
"You got the face."
"What face?"
"The I'm-about-to-take-apart-every-electronic-device-in-the-house face."
Tony looked offended.
"I don't have a face."
"You absolutely have a face."
Tony tapped the bracelet.
The blue indicator pulsed at exactly the same rhythm as the glow beneath his shirt.
His expression changed.
"It matches me."
Howard crouched in front of him.
"It helps your nervous system regulate how much energy you're sending outward."
Tony looked at his chest.
Then the bracelet.
"So it's connected to my reactor?"
"Everything is connected to your reactor."
Tony thought about that.
"My heart too?"
Howard paused.
He could have given him the scientific explanation.
Tony probably would've understood half of it already.
Instead Howard placed his hand gently against his son's chest.
Underneath his palm were two rhythms woven together.
The beat of Tony's natural heart.
And the quiet pulse of Extremis.
"Your heart and your reactor grew together," Howard said. "Neither one is some machine somebody put inside you. They're both part of you."
Tony looked down.
"So I have two hearts?"
Howard smiled.
"In a manner of speaking."
Tony's eyes lit up.
"That's awesome."
Howard laughed.
"Yeah."
He looked at his son.
"It kind of is."
The Stark garage became Tony's favourite place in the world.
It smelled like oil, hot metal and whatever expensive aftershave Howard had used that morning.
Vintage cars lined the walls like sleeping dragons.
Howard had Tony sitting on the workbench wearing goggles much too large for his face.
AC/DC blasted from an overworked speaker.
Howard opened the hood of a Ford Roadster.
"Engines are basically alive."
Tony immediately frowned.
"No they're not."
Howard stared at him.
"You're four."
"And you're wrong."
Howard slowly smiled.
"Okay, smartass. Engines behave like they're alive."
"Better."
"They breathe. They eat fuel. They create heat. Every component has to work with every other component."
Tony leaned forward.
Howard pointed.
"Carburetor."
Tony inspected it.
"What's wrong with it?"
"You tell me."
Tony listened.
Not merely with his ears.
Something inside him reached outward.
He couldn't explain it yet.
Machines weren't alive.
He knew that.
But they had patterns.
Electrical currents.
Mechanical rhythms.
Signals.
And Tony could somehow feel when the rhythm was wrong.
He pointed.
"There."
Howard's smile disappeared.
Tony pointed directly toward the fault.
"It's choking."
Howard looked at him.
Tony shrugged.
"This car has asthma."
Howard burst out laughing.
"Then let's give her better lungs."
From upstairs came Maria's voice.
"Howard Anthony Stark!"
Both boys froze.
Maria appeared.
She looked at the speaker.
Then Howard.
Then her four-year-old son nodding along to Back in Black.
"Really?"
Howard shrugged.
"He likes it."
"He's four."
"He has excellent taste."
"Try lullabies."
"Too slow for science."
Jarvis appeared behind Maria.
Tony looked toward him.
"Jarvis likes it."
Jarvis paused.
Four adults' eyes landed on him.
The butler considered his options carefully.
"I believe Master Anthony has discovered his preferred tempo."
Tony pointed triumphantly.
"See?"
Maria closed her eyes.
She was surrounded.
Tony met T'Challa when they were eight.
The Stark jet descended through Wakandan airspace while Tony had his face practically pressed against the window.
Howard looked over.
"Try not to embarrass America."
Tony didn't move.
"You embarrass America all the time."
Maria covered her mouth.
Howard stared at his son.
Jarvis looked very interested in the seatbelt instructions.
"Whose side are you on?"
Tony finally looked around.
"Mine."
Howard nodded slowly.
"Definitely my kid."
Wakanda fascinated Tony immediately.
Not because it was beautiful.
It was.
Not because of the technology.
Although that nearly broke his brain.
It was the vibranium.
The moment Tony entered the royal laboratory, his reactor changed pitch.
T'Challa noticed.
The Wakandan prince was almost Tony's age but carried himself completely differently.
Tony moved like his thoughts were trying to outrun his body.
T'Challa watched before acting.
"You're making that sound," T'Challa said.
Tony looked down.
"My reactor does that."
"Why?"
Tony looked toward a piece of vibranium.
"Because of that."
He approached it.
Howard noticed.
So did T'Chaka.
Tony touched the metal.
HMMMMMMMMM.
His reactor responded instantly.
But Tony's skin didn't transform.
He didn't become vibranium.
Instead he felt the metal.
Its molecular vibration.
Its ability to absorb energy.
The way energy moved through it.
Extremis flooded Tony's brain with information faster than he consciously understood.
Tony jerked his hand away.
T'Challa stepped closer.
"What happened?"
Tony stared at the vibranium.
"It stores energy."
T'Challa smiled slightly.
"Yes."
"No."
Tony looked at him.
"I mean it remembers where the energy went."
T'Challa's expression changed.
Now Tony had his complete attention.
Howard and T'Chaka exchanged a glance across the laboratory.
Neither boy noticed.
They were already talking.
Already arguing.
Already building.
And by dinner, Tony had decided Wakanda needed something critically important.
Better music.
He placed a tiny Stark speaker on the table.
T'Challa looked suspicious.
"What is that?"
"Culture."
Tony pressed play.
AC/DC erupted across the royal dining room.
T'Challa stared at him.
Then started laughing.
Within seconds both boys were nodding along.
Maria slowly turned toward Howard.
Ramonda slowly turned toward T'Chaka.
The two husbands wisely avoided eye contact.
Ramonda finally looked at Maria.
"Your son's energy appears contagious."
Maria sighed.
"So is his volume."
Howard raised his glass.
"Let them be loud."
He watched Tony and T'Challa laughing.
"They're the sound of tomorrow."
Professor Hikari Sato entered Tony's life shortly afterward.
She wasn't an engineer.
That was precisely why Howard hired her.
Howard could teach Tony machines.
Sato taught Tony himself.
"You keep treating your Quirk like a machine," she told him.
Tony sat cross-legged across from her.
"It has a reactor."
"So?"
"Reactors are machines."
"Is your brain a machine?"
Tony immediately answered.
"Technically—"
"No."
Tony frowned.
Sato smiled.
"Your father teaches you how things work. I'm going to teach you how you work."
That was considerably harder.
Tony could dismantle an engine.
He could rewrite software.
He could understand a circuit after looking at it once.
But emotions?
Those were messy.
And Extremis reacted to them.
Anger increased energy production.
Fear accelerated his nervous system.
Excitement caused his technological interface to reach outward.
Pain activated regeneration.
Tony had spent his entire childhood trying to control the reactor.
Sato taught him something different.
The reactor wasn't misbehaving.
Tony was communicating.
He simply hadn't learned the language yet.
"Breathe."
Tony inhaled.
His chest brightened.
"Listen."
He exhaled.
The light dimmed.
Again.
Again.
Again.
Eventually Tony could feel every pulse of energy moving through him.
His heartbeat.
His reactor.
His bloodstream.
His nerves.
Not separate systems.
One body.
One Quirk.
Extremis.
The breakthrough came accidentally.
Howard was working late.
Tony found him staring at a holographic model of Stark Tower's new reactor grid.
Red warnings covered half the display.
Tony climbed onto the stool beside him.
"That's wrong."
Howard didn't look away.
"Bed."
"Your tertiary coils are overloaded."
"Bed."
"Three microseconds."
Howard stopped.
Slowly turned.
"What?"
Tony pointed.
"That delay."
Howard enlarged the simulation.
Tony was right.
Howard stared at him.
"How did you see that?"
Tony shrugged.
"I didn't."
Howard frowned.
Tony looked toward the hologram.
"I felt it."
Then the strangest thing happened.
Tony's reactor brightened.
The hologram flickered.
Howard's hands weren't touching the controls.
Neither were Tony's.
Lines of code began moving.
Howard froze.
"Tony."
"I know."
"You're inside the system."
"I know."
"Get out."
"Dad—"
"Tony."
Tony disconnected instantly.
The hologram stopped.
Silence.
Tony looked worried.
Howard wasn't angry.
He was terrified.
Not of Tony.
For Tony.
Howard crouched.
"Did that hurt?"
"No."
"Headache?"
"No."
"Dizzy?"
"No."
"You hear anything?"
Tony thought.
"The building."
Howard stared.
"What do you mean, you hear the building?"
Tony struggled for words.
"The cameras. Elevators. Lights. Computers."
His reactor hummed softly.
"They're talking."
Howard looked toward the enormous Stark Industries network surrounding them.
Then back at his eight-year-old son.
"And you understand them?"
Tony smiled.
"Dad."
Howard knew that smile.
Oh, God.
"What?"
"I think computers are easy."
Howard stared at him.
Then laughed despite himself.
"Of course you do."
They turned back toward the reactor simulation.
Tony pointed.
"Can I fix it?"
Howard considered the question.
Then pulled another chair over.
"Together."
Tony grinned.
Together, they rebuilt the system.
When the final warning changed from red to blue, Howard leaned backward.
Tony yawned.
"You just corrected a power system designed for half of Manhattan."
Tony rubbed his eyes.
"Make the lights pulse."
"What?"
"Like this."
Tony tapped his chest.
Thump.
Hum.
Thump.
Hum.
"People won't understand reactors," Tony said. "But everybody understands a heartbeat."
Howard looked at his son for a long moment.
Then smiled.
"Okay."
Tony climbed down.
"I'm going to bed."
"Tony?"
He turned.
Howard looked at the completed design.
"Good work."
Tony grinned.
"Obviously."
After Tony left, Howard saved the design.
PRIMARY_HB_01.tny
Heartbeat One.
The years that followed changed Stark Industries.
Howard still built machines.
Tony started asking who those machines were supposed to help.
Together they developed micro-reactors for hospitals.
Advanced prosthetics.
Adaptive support equipment for heroes whose own Quirks damaged their bodies.
Heat-resistant equipment for fire users.
Pressure-dispersing gauntlets for explosive Quirks.
Impact-resistant footwear for speedsters.
Medical equipment capable of surviving electromagnetic Quirks.
And eventually—
HeroFibres.
Tony stood before a room filled with Stark engineers.
He held up a strip of adaptive fabric.
"Most support equipment treats the person like they're the problem."
The room went quiet.
Tony continued.
"Too much heat? Contain them. Too much force? Restrain them. Electricity? Insulate them."
He shook his head.
"Wrong approach."
Howard watched from the back.
Maria stood beside him.
Tony tapped the fabric.
"The equipment should adapt to the person. Not force the person to adapt to the equipment."
A holographic simulation appeared.
The fabric changed tension, conductivity and heat resistance around a simulated Quirk activation.
Tony smiled.
"Every thread listens to its wearer."
Howard looked at Maria.
She was already looking at him.
"He's changing your company," she whispered.
Howard watched his son.
"No."
There wasn't jealousy in his voice.
Only pride.
"He's building his own."
Years after that first storm, Howard and Tony stood together on the balcony of Stark Tower.
New York stretched beneath them.
Blue-white reactor energy illuminated entire districts.
Hospitals.
Schools.
Homes.
Hero agencies.
Subways.
Millions of people benefiting from technology Tony had helped create before he was old enough to legally drive.
Howard leaned against the railing.
"When I was your age, I wanted to become the smartest man alive."
Tony glanced over.
"And?"
Howard smiled.
"Then you came along."
Tony smirked.
"So second-smartest isn't bad."
Howard stared at him.
"I walked directly into that one."
"You really did."
For a while neither spoke.
Tony's heart beat.
His reactor answered.
Thump.
Hum.
Howard looked toward Stark Tower.
The building's illumination slowly brightened.
Then dimmed.
Exactly according to Tony's rhythm.
People down on the streets looked upward.
Most assumed it was decorative.
Some thought Stark Industries was showing off.
Howard knew differently.
Twenty years earlier, doctors had looked at his newborn son and seen something impossible.
A child whose biology and technology had somehow become one.
Howard had looked at Tony and wondered whether the world would ever understand him.
Now he finally understood something himself.
The world didn't need to understand Tony Stark yet.
It just needed enough time to catch up.
From somewhere inside the tower, AC/DC started playing.
Howard sighed.
"You've connected yourself to the building's speakers again."
Tony smiled.
"I have no idea what you're talking about."
"Turn it down."
"No."
"Tony."
"It's scientifically necessary."
Howard laughed.
Below them, New York continued glowing.
And Stark Tower pulsed again.
Thump.
Hum.
Not the heartbeat of a machine.
Not even just the heartbeat of Tony Stark.
It was the first heartbeat of a world he was already beginning to build.