The door clicked shut with the finality of a verdict, and the corridor seemed to hold its breath. The torchlight guttered, shadows stretching long across the stone as if the flames themselves had flinched. Nico stood motionless, his hand still wrapped around the hilt of his blade, his knuckles pale against the worn leather grip. His amber eyes never left the oak grain of Vane's door, tracing its whorls and knots as though they might part and show him what was happening on the other side.
The oath thrummed in his chest, a second heartbeat that wasn't his. Cleo's pulse, distant but unmistakable, quickened as she stepped deeper into the office. He could feel her fear before she could name it, a cold thread winding through the bond they'd sealed in blood. It made his jaw tighten, made the wolf beneath his skin shift and pace.
"She'll be fine," Sera said, her voice too high, too quick. "Vane wouldn't—he's her professor, he wouldn't—"
Nico didn't turn. "You don't believe that."
The silence that followed was answer enough. He heard Sera shift her weight, heard the soft rustle of her robes as she moved closer to the wall, her fingers already drifting toward her wand. Her green eyes were wide in the torchlight, the mischief that usually lived there gone, replaced by something sharper, older.
"I believe he's scared," she said finally. "And scared men do stupid things."
The growl came from beneath the floorboards.
It started low, a vibration Nico felt through the soles of his boots before he heard it—a sound that wasn't quite animal, wasn't quite stone grinding against stone. It swelled, closer than it had been in the corridor before, hungrier, and the torch flames bent toward it as if drawn by an invisible breath.
Sera's face went pale. Her hand closed around her wand, knuckles whitening. "That's not the wolves," she whispered.
Nico's heartbeat spiked through the oath—his own, or Cleo's, he couldn't tell anymore. He felt her fear answer it from the other side of the door, a sharp echo that made his ribs ache. The growl deepened, vibrating through the mortar, through the old stones, through the marrow of his bones. It was a sound that knew him. That was reaching for him.
"What is it?" he asked, his voice low and controlled, the voice he used when he was one breath from violence.
Sera shook her head, red curls brushing her shoulders. "I've heard it before. In the old tunnels, the ones that run under the west wing. But never—" She swallowed. "Never this close."
The growl shifted. Rose in pitch. Almost formed a syllable.
Nico's hand left his blade. His jaw set, a muscle jumping beneath the scar that crossed his brow. He took one deliberate step toward the source of the sound, his boot scraping against the stone, and the corridor's silence shattered around him like a pane of glass.
"It knows your name," Sera breathed.
The words hung in the damp air, and Nico felt them land somewhere deep, somewhere the wolf understood even if the man didn't. The growl beneath the floorboards answered his step—not with retreat, but with a shift in pitch, a sound that was almost a word, curling up through the cracks in the stone like smoke.
He stopped. His amber eyes dropped to the floor, scanning the seams between the flagstones, looking for the source of a sound that shouldn't exist. The wolf in him was on high alert, every sense stretched taut, listening for the thing that hunted in the dark beneath the castle.
"It's not coming from the tunnels," Sera said, her voice barely a breath now. "It's coming from—" She stopped, her green eyes fixed on a point just past Nico's shoulder.
He turned, following her gaze. The torch on the far wall was flickering in a pattern that felt deliberate, almost rhythmic, as if the flame itself were trying to speak. The shadows it cast writhed across the stone, forming shapes that dissolved before the eye could name them.
The growl came again, closer now, and this time Nico heard it for what it was.
A name. His name. Spoken in a voice that was not human, not wolf, not anything that should have known it.
"Nico."
The word rose from the floorboards, soft as a prayer, sharp as a blade. Sera's wand was in her hand, a whispered curse half-formed on her lips as the torch flames bent toward the sound, and Nico felt the oath flare in his chest—Cleo's fear, his own, tangled together in a knot he couldn't untie.
He took another step. The growl answered, not with retreat, but with something that might have been a laugh.
The door behind him opened.
Nico spun, his hand finding his blade again, the motion fluid and instinctive. But it was Cleo who stood in the threshold, her gray eyes wide, her silver-blonde hair catching the torchlight like spun moonlight. She looked past him, past Sera, to the floor where the growl had been, and her face went very still.
"I heard it," she said. "Through the oath. I felt—" She stopped, her hand pressing against her chest, over the place where his heartbeat lived. "Nico, what is that?"
He didn't have an answer. The growl had gone quiet, but he could still feel it, a pressure in the air, a weight in the stone. It was waiting. Listening. Watching through eyes that weren't there.
"It knows your name," Sera repeated, and this time there was no breath in her voice, only a flat certainty that made the torchlight seem dimmer. "It's been waiting for you."
Cleo's hand found his arm. Her fingers were cold, trembling, and the oath carried her fear into his chest like a flood. He covered her hand with his own, felt the dried blood on both their palms flake and shift, a reminder of what they'd sworn.
"Whatever it is," he said, his voice low and steady, "it can wait. We have a price to name."
He looked past Cleo, into the office where Vane stood in the lamplight, his immaculate robes catching the glow, his scarred hands folded before him. The professor's blue eyes were fixed on the corridor, on the floor, on the space where the growl had been. His face was unreadable, but Nico saw the way his jaw tightened, the way his fingers pressed together just a little too hard.
"Close the door," Vane said. His voice was calm, measured, but there was an edge to it that hadn't been there before. "We have much to discuss."
Cleo stepped back into the office, pulling her hand from Nico's grip. She looked at him once, a long look that said everything and nothing, and then the door was closing, the oak swinging shut with a sound like a tomb sealing.
Nico stood in the corridor, staring at the wood grain. The growl was still there, beneath his feet, beneath the stone, a pulse in the earth that matched the pulse in his chest. It knew his name. It had been waiting for him.
And somewhere beyond the door, Cleo was walking deeper into the office of a man who had named a price for their bond.
Sera's hand was on his arm, her grip surprisingly strong for someone so small. "Nico," she said, her voice low and urgent. "That thing under the floor. I've heard it before, but never like this. Never—" She stopped, her green eyes searching his face. "It was calling you. Not threatening. Calling."
He didn't answer. He couldn't. Because she was right, and he knew it, and the knowing sat in his chest like a stone.
The torch flames flickered. The growl stirred, soft and low, almost contented. And through the oath, Nico felt Cleo's heartbeat slow, steady, as if the thing beneath the floor had reached through the stone and touched her too.
"We need to move," Sera said, her voice sharp. "Now. Before it decides to come up."
Nico didn't move. His amber eyes were fixed on the door, on the space where Cleo had stood, on the echo of her heartbeat in his chest. The growl hummed beneath his boots, a sound that was almost a word, almost a name, almost a promise.
"She's in there," he said. "With him. And I'm out here."
Sera's grip tightened. "She chose this. She walked in there knowing what she was doing."
"That doesn't make it right."
"No," Sera said quietly. "It doesn't. But it makes it hers."
The words landed like a blow. Nico's jaw tightened, his hands curling into fists at his sides. He wanted to break down the door, to pull Cleo out, to drag her somewhere the wolves couldn't reach, where Vane couldn't bargain, where the thing under the floor couldn't whisper his name.
But Sera was right. Cleo had walked in there alone, knowing the price, knowing the risk. She had chosen this, the same way she had chosen the oath, the same way she had chosen him.
And he had to trust her.
The growl beneath the floorboards shifted again, a sound that was almost a sigh, almost a laugh. It knew something they didn't. It was patient.
Nico turned away from the door, his hand finding the hilt of his blade again. The torchlight flickered, the shadows writhed, and somewhere beneath the castle, something with a voice like grinding stone settled back into the dark to wait.
"Guard the corridor," he said to Sera, his voice flat. "I'm going to find out what that thing is."
Sera's eyes widened. "Nico—"
"Guard it," he repeated. "If anything comes through that door that isn't Cleo, you know what to do."
He didn't wait for her answer. He walked past her, toward the far end of the corridor, where the torch flames bent toward the dark and the growl had gone quiet. His boots scraped against the stone, and the sound echoed in the silence like a challenge.
The thing beneath the floor had called his name. It had been waiting for him.
He intended to find out why.
The corridor narrowed as he walked, the walls pressing closer on either side, the torch sconces spaced farther apart until the light came in pools rather than a steady wash. Nico's boots found the old stones with a rhythm he didn't have to think about, the hunter's gait that kept his weight balanced, his senses spread wide. Behind him, Sera's footsteps followed, lighter, quicker, a counterpoint to his own.
"You're not supposed to be following me," he said without turning.
"You're not supposed to be walking into whatever that thing is without someone watching your back." Her voice had lost its sharp edge, settling into something almost practical. "Besides, you told me to guard the corridor. The corridor's this way too."
He stopped at a junction where the passage branched left into darkness and right toward a spiral staircase he'd never taken. The growl was fainter here, but not gone—a vibration he felt more than heard, like a distant waterfall moving through the earth. He pressed his palm flat against the stone wall, felt the cold seep through his calluses, and waited.
Nothing. Just the stone, the damp, the faint tremor of something below.
"It's not under this part of the castle," Sera said, stopping a few paces behind him. She'd drawn her wand, holding it loosely, the way someone held a pen they didn't intend to use yet. "The sound's coming from deeper. The old foundations, maybe. The parts they sealed off."
"You've been down there."
"Once." She said it flatly, without elaboration, and he knew better than to ask for more.
The torch beside them guttered, the flame drawing thin and tall, bending toward the dark passage on the left. Nico watched it, noting the way it leaned, the way the shadows stretched long and hungry in that direction. The corridor itself seemed to be pointing.
"It's waiting for us," he said. Not a question.
Sera's jaw tightened. "It's waiting for you."
The words sat between them in the damp air. Nico let them settle, let their weight press against his ribs, and then he turned left, into the dark, where the torchlight didn't reach and the growl pulsed like a heartbeat in the stone.
The dark swallowed him whole. His eyes adjusted slowly, the wolf in him lending an edge to his vision that the man alone wouldn't have had. He could make out the shape of the passage—rough-hewn walls, a ceiling that dipped low enough to brush his hair, flagstones worn smooth by centuries of feet that no longer walked here. The air was colder, carrying a mineral smell, like wet rock and old iron.
Behind him, Sera's breath came quick and shallow. "Nico, I don't—"
"Shh."
He stopped. Listened. The growl was closer now, not louder but more present, as if the space between them and it had collapsed. It hummed through the soles of his boots, through the walls, through the dark itself. And beneath it, another sound—a rhythm, steady and slow, like something breathing.
His hand found the hilt of his blade, the leather grip familiar against his palm. He didn't draw it, not yet, but the weight of it was a comfort, a promise he could keep if he needed to.
The passage opened into a wider chamber, the ceiling vaulting overhead into shadow. Torches lined the walls here, unlit, their sconces black with old soot. In the center of the floor, a circle of stones—rough, unmarked, older than the castle itself—lay arranged in a pattern that made the wolf in him want to step back.
The growl came from beneath those stones.
"That's not a tunnel," Sera said, her voice barely above a whisper. "That's a seal."