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It starts, like all things do, with Sirius leaving.
Regulus had begged him. On his knees, bruised and raw, a shell of himself, he'd asked Sirius not to go — not to leave him alone in that house with their parents. But Sirius had left anyway, running off to the Potters, leaving Regulus behind to rot.
Remus was the only one who stayed.
Remus Lupin, soft-spoken, always in the background, the "nice one" of the group. But there was something sharp in him, something dark, something everyone liked to ignore.
When he found Regulus after Sirius left — broken, cold, barely hanging on — Remus decided to never let anyone hurt Regulus again.
And if they had?
They'd pay for it.
The First Deaths: Evan and Barty
“Hello, Evan,” the voice on the other end of the phone purrs. Mechanical, distorted. Smooth like silk wrapped around a blade.
“Who the hell is this?” Evan snaps, rolling his eyes as he glances around his flat.
“Do you like scary stories?”
It’s a joke, Evan thinks. Right up until he steps into his kitchen, and Regulus Black is standing there, wearing a Ghostface mask — but his eyes, oh, his eyes are cold and murderous.
Evan barely has time to scream before Regulus moves fast — knife plunging into him with sharp, precise cruelty.
Remus had told him exactly how to do it.
The next day, Barty’s body is found — throat slit, tied to a chair, a mockery of love letters Regulus had written him scattered around.
Remus and Regulus watched the scene from afar, hands clasped tightly, as if Barty and Evan’s deaths were poetry only they understood.
James and Peter
James dies because he flirts. Too many sweet smiles and hands on Regulus’ arm, and Remus can't have that.
So when James is alone, heading home from practice, Remus slips behind him in the Ghostface mask.
The last thing James hears is, “You should have stayed away from him.”
Peter is easy. Always following Sirius, always poking where he shouldn’t.
Remus corners him in the library after hours, blade slipping into his ribs as he whispers, “Wrong place, wrong time, Wormtail.”
Dumbledore — for Safety
Dumbledore starts to suspect.
Regulus handles this one — a quick slash to the throat in his office late one night.
“For Remus,” he whispers to the corpse, wiping the blood off his blade.
The Final Game: Sirius
The grand finale, the one Regulus made Remus promise to save for last.
Sirius is haunted by the deaths swirling around them — and the killer is getting closer.
He never suspects his own brother, or quiet Remus.
When Sirius gets the call — that call, that same twisted voice — he runs to the abandoned house on the edge of town.
Ghostface waits. But when he rips off the mask — it’s not just one.
It’s both of them.
“Regulus?” Sirius’ voice cracks, confused and hurt.
Regulus steps closer, mask hanging in his hand. His eyes are wild but shining.
“You left me,” he whispers, voice broken. "You let them hurt me."
Remus moves beside him, calm, deadly, resting a hand on Regulus’ waist. “You don’t deserve him. You never did.”
Sirius steps back. “Remus? You—
"
“Always loved him," Remus says simply. "Always wanted to protect him.”
Sirius laughs bitterly. “By killing everyone? You’re insane.”
Regulus tilts his head. “Maybe. But at least I’m not alone.”
When they strike — they strike together. Two knives, two blades — twin smiles as Sirius goes down.
After
The town mourns, whispers flying, rumours blooming like rot.
Remus and Regulus walk through it all hand-in-hand, clean and untouched — the grieving friends of the victims.
Regulus smiles quietly, always at Remus’ side, the picture of someone who has finally been "saved."
But behind closed doors, when they're alone, Regulus laughs — sharp, soft, dangerous — as Remus kisses his knuckles, holding him like he’s something precious and untouchable.
Because now, no one will ever hurt him again.
And if anyone tries?
Well, they still have the mask.
"He’s so evil," Regulus murmurs, watching Remus trace lazy circles on his thigh.
"Look at that stare. Nothing behind those eyes."
He leans down, presses a kiss to Remus’ jaw, and smiles against his skin.
"God, I want him."
And Remus just smiles back — dangerous, sharp, and hopelessly in love.