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Night's Heir - The Hyde Within

Summary:

After a different outcome to the experiment in 1990, Isaac Night survives and dedicates his life to science and to protecting his family without risking the life of another. When his sister Francoise dies, leaving her young son Tyler in the care of an absent father, Isaac becomes both guardian and mentor. As Tyler begins to awaken to his Hyde nature, Isaac guides him through the challenges of adolescence, supernatural abilities, and a legacy of power and danger. However, nobody said it was easy to trick destiny.

Notes:

Hello everybody!
I just love the character of Isaac Night and wanted to see more of him - so I decided to write my own story about him exploring the relationship with Tyler in this AU.

This fanfiction was inspired by the story "Uncle Isaac AU" by Lor3na_ilm26xx but I hope it is obvious that I gave it a different spin, especially in portraying Isaac's character.

Have fun reading! I would love some feedback in the comments or kudos.

Chapter 1: One Night Survives

Chapter Text

Night's Heir

The Hyde Within

Chapter 1: One Night Survives

 

Jericho, Autumn of 1990

Leaves drift in gold and copper swirls across the courtyard of Nevermore Academy on this crisp autumn afternoon. Isaac Night stands hunched over a drafting table in his well-used lab in Iago Tower, dim light from a single lamp illuminating blueprints sprawled in front of him. His clockwork heart beating with a soft tick tick tick having outlived everyone’s expectations of his death four years ago. Francoise enters quietly, her footsteps muffled on wooden floorboards. She holds two mugs of cocoa.

“Still at it?” she asks, setting one down beside Isaac. Steam curls into the air.

Isaac glances up, a faint smile. “You know me — I’ve got designs to finish.”

His fingers trace the outline of a big engine – his chance to cure his sister of her curse.

Francoise watches him, admiration and worry in her dark eyes. “Do you think it will work?”

He pauses, pencil hovering. “I do.”

In another life he would leave it at that. Would promise his sister to finally cure her of the monster inside of her. To keep the secret of the cost as his burden to carry. But in this one he straightens and looks at Francoise again.

“I fear there will be a heavy price to pay, Francoise.”

His sister’s eyes widened in concern. “What is the price? Will it harm you?”

A short humorless laugh escapes Isaac. “Not me. The machine needs a very strong power source. There is nothing strong enough I can think of besides… the power of a Spark.”

Francoise looks at him, trying to follow her brothers line of thought. She couldn’t think of a reason why that would be a problem yet.

“But you know a Spark. Gomez is one, isn’t he? And he is your best friend. He would help you.”

Her younger brother sighs again, his eyes now downcast. “The machine would need all of his power. I fear he wouldn’t survive, Franny…”

She gasps, staring down at the blueprint of her only hope in fear. Of course she would love to be cured, to finally be rid of the curse that haunts her so relentlessly. But could she do it at the cost of another’s life?

“No… Isaac… we can’t do that. Not to Gomez, not to anyone. If that is the cost I don’t want it. Maybe you will find another way one day…”

Isaac looks at her, the sadness in his gaze obvious. “I know I promised you, Franny… I will try to find another way.”

He takes her hand in his and presses it firmly. Over the next years, Isaac works tirelessly. Late-nights, whispered lectures with sympathetic professors, experiments that almost go wrong (a blown fuse here, overheating core there). Nevermore alumni begin to speak of him: the boy who repaired broken things — hearts, machines, even broken scientific laws. By 2002, he’s published a paper on bio-mechanical heart augmentations that draws attention from medical researchers worldwide. He sets up a modest lab in Boston, gains funding, wins awards. Yet he makes no new progress in regard to what matters most to him – finding another way of curing his sister’s Hyde side.

 

Jericho, Summer of 2004

A lush garden with tulips and cherry blossoms in bloom waits just outside of Jericho for the special event planned for today. Isaac — in a tailored dark suit, crisp shirt, tie just dark violet — stands near a trellis draped in white roses. He’s cleaner than the Nevermore lab boy of old; the hands that once tinkered under flickering lamps are now steady, confident. His clockwork heart, upgraded twice, hidden beneath the chest, ticks in a quiet harmony with his own pulse.

Francoise walks down the aisle in a soft gown, her eyes shining. Donovan Galpin — Francoise’s longtime partner and new sheriff of Jericho — waits at the altar. Isaac’s chest tightens — proud, protective, hopeful. He gives Francoise a small nod, as though their shared past, all the secret nights of invention and worry, have led here. He has his doubts regarding his sister’s wish to marry a Normie who knows nothing about her inner beast. But what kind of brother would he be to deny her the wish for normalcy that he himself is not able to fulfill yet.

He watches his sister and her fiancé taking their vows, staring love-struck into each other’s eyes until they are finally pronounced husband and wife followed by loud applause.

At the reception guests talk in low hums: colleagues of Donovan, friends, and a scattering of Isaac’s scientific peers who came to congratulate. Isaac is approached by a distinguished researcher from Geneva, Dr. Aurelia Weber, who compliments him on his latest publication.

“You’ve done remarkable work, Isaac. The augmentation design for synaptic regenerative tissue — it’s remarkable.”

She raises her glass. Isaac smiles, lifting his own.

“Thank you. None of it would be possible without Francoise’s early encouragement... or the many nights in Nevermore when ‘fragile’ meant fight.”

Francoise comes up behind them, slipping her hand into his. Isaac turns; she gives him a knowing smile. People laugh, dance, soft jazz in the background. For a moment, Isaac catches Donovan’s eye; they nod in mutual respect — Donovan, grateful Isaac was there; Isaac, grateful to see his sister so happy.

Outside, lanterns glow, the air scented with flowers. Isaac steps onto the terrace, looking up at the sky. He pulls a small notebook from his pocket — scribbled ideas. Always the mind of the future, even in celebration. Francoise joins him.

“You’ve built more than machines, Isaac,” she says softly. “You’ve built trust, healed wounds.” Isaac closes the notebook.

“I only ever wanted to make things right. You deserve that.&rdquo They stand there, amid laughter and music, while Isaac lets himself believe perhaps the future will be kinder, that knowledge can be a safeguard, not a danger.

 

Jericho, Spring of 2006

The hospital smells faintly of antiseptic and fresh paint. Rain taps lightly against the tall windows as Isaac steps into the small maternity ward room, carrying a bouquet of pale lilies. Francoise is propped up against crisp white pillows, hair messy but glowing with exhaustion and pride. In her arms, wrapped in a soft blue blanket, lies her son — Tyler.

Isaac hesitates at the door. His clockwork heart ticks faintly, audible only to him, like a reminder of all the battles he’s fought to survive. Francoise spots him instantly, smiling wearily.

“About time, Professor Night. Come meet your nephew.” Isaac crosses the room, setting the flowers on a side table before leaning closer. Tyler’s tiny face is peaceful, fists balled up like he’s already ready to fight the world.

“He looks… impossibly small”, he says softly but Francoise only smiles.

“He’s strong. Stronger than I ever was.”

Half-smiling Isaac looks to her again, “That’s what I’m afraid of.”

Francoise glances up sharply, reading his tone. “Isaac… don’t.”

“We both know what runs in our blood. You’ve managed it — mostly. But what if—” He gestures at the baby, “—he doesn’t?”

Francoise shifts Tyler protectively against her chest. “He’s not me. And he won’t be you either. He’ll be his own person. Donovan and I will raise him right, give him stability, love. That matters more than… genes.”

“Love doesn’t change biology, Francoise. A Hyde is a Hyde. You know that better than anyone.”

Her jaw tightens, but her voice stays calm, almost pleading, “You don’t understand, brother. I control it. I’ve lived with it, I’ve chosen not to give in. You think I’m broken, something to be ‘fixed,’ but maybe I’m just… me.”

Isaac looks away, his hand tightening around the edge of his coat. He still hasn’t found a way to cure her. And now there might be another little part of Francoise facing the same burden.

“I don’t think you’re broken. I think you deserve peace. I’ve spent years proving machines can heal, that blood and gears can coexist. If I could stabilize the heart in my chest, why shouldn’t I find a way to cure what twists yours?”

Francoise exhales, tired but resolute. “Because it’s not just a disease, Isaac. It’s a choice. My Hyde isn’t some infection — it’s part of me. I choose not to let it control me. Tyler will have that same choice, if it even comes to him.”

Isaac studies the child again. Tyler stirs, tiny eyelids flickering. Isaac’s voice softens.

“And what if he doesn’t? What if one day he wakes up and there’s no choice, only the monster?”

Francoise’s eyes harden, protective fire flashing in them.

“Then he’ll have me. And he’ll have Donovan. And if the worst comes to pass… he’ll have you too. Not as a scientist trying to ‘cure’ him. As his uncle. Promise me that, Isaac.”

The ticking in Isaac’s chest grows louder to his ears. He meets her gaze, torn between conviction and love. After he pause he finally answers.

“I promise… I’ll be whatever he needs.”

Francoise relaxes slightly, resting her cheek against Tyler’s head. The baby lets out a tiny sigh, as if sealing the vow between them.

“Good. Because I don’t want him growing up thinking he’s some experiment waiting to happen.”

Isaac smiles faintly, despite himself.“He’ll grow up thinking he’s the most stubborn Night in the family. And that’s saying something.”

They both laugh quietly, though the weight of their words lingers in the sterile air. Isaac watches Tyler one last time before stepping back. Deep down, though he promised his sister, his mind is already working — calculations, theories, possibilities. The cure isn’t abandoned. Not yet.

 

Jericho, Spring of 2010

The church in Jericho was small, tucked between the rolling hills and the riverbank, its stone walls weathered by centuries of wind. Black ribbons hung heavy against the white doors. Inside, the pews were filled with familiar faces: townsfolk whispering condolences, Nevermore alumni who remembered Francoise as both brilliant and haunted. Isaac sat near the front, hands clasped together, the faint whir of his clockwork heart betraying his tension.

He had buried himself in journals and machines when the news first came — Francoise, gone at only thirty-six. Her body had simply given out, weakened by the constant strain of living with a Hyde’s curse. Isaac had seen it coming, but he had not been ready. He doubted he ever would have been.

Tyler sat beside him, too small for his dark suit, eyes wide and glassy. Donovan Galpin stood at the lectern, reading words that sounded more like obligation than grief. His voice was steady but hollow, as though his duty as sheriff had bled into his role as husband and father.

Isaac looked at Tyler, who stared at the floor with the detached gaze of a child who didn’t yet understand permanence at only four years of age. After the service, when the casket was carried out under the gray sky, Isaac stayed behind with his nephew.

“Tyler,” he said gently, kneeling down so they were eye level.

The boy’s eyes flicked to him, uncertain, wary.

“She’s not coming back, is she?” Tyler asked, his voice small and almost swallowed by the murmurs of the crowd outside.

Isaac swallowed hard. “No. But she’s not gone either. She’s here.” He tapped Tyler’s chest softly. “Every time you laugh like her, or get that stubborn frown she always wore when she was right — and she usually was — she’ll be there.”

Tyler frowned, chewing his lip. “Dad doesn’t talk about her. He just… works.”

Isaac’s jaw tightened. He glanced through the open doorway, where Donovan shook hands with townsfolk without looking at his son.

“Your father grieves differently. Sometimes… people hide from pain by burying themselves in other things.”

“But I don’t want to hide,” Tyler said, his voice cracking. “I just want Mom.”

Isaac pulled him into his arms, holding him tighter than he thought his fragile body would allow. The ticking in his chest steadied, a mechanical lullaby against the boy’s ear.

“I made your mother a promise,” Isaac whispered into his nephew’s hair. “That I’d be here for you. I won’t let you be lost, Tyler. Not while I still breathe.”

Tyler clung to him then, silent sobs shaking his small shoulders. Isaac closed his eyes, grief crashing down in waves. He had failed his sister’s fragile body, but he would not fail her son. When they stepped back into the pale light of the graveyard, Isaac placed a hand on Tyler’s shoulder.

"You and I,” he said quietly, “we’re Nights. And Nights don’t disappear. We endure.” Tyler nodded faintly, his face streaked with tears, and for the first time since the casket had closed, Isaac thought he saw a spark of his sister in the boy’s eyes.