The air at the edge of the Underworld tasted wrong.
Not sulfur, not smoke—something colder. Like breath held too long. Percy felt it first as a pressure behind his eyes, a heaviness in his chest that had nothing to do with exhaustion. The cavern yawned open before them, a vast arch of black stone carved with scenes of suffering so old they'd been worn smooth by time. Beyond it, darkness pulsed, slow and steady, like a sleeping giant.
"This is it," Grover whispered.
Cynthia stood slightly ahead of the group, posture still, knives sheathed but hands loose at her sides. Her winged shoes were quiet—too quiet. She didn't like that. Instinct crawled along her spine.
Annabeth unfolded the map of the Underworld, fingers trembling despite her effort to keep them steady. "The Fields of Asphodel should be past the gate. Then the palace."
Percy nodded, but his attention drifted to the river beside them—the Styx, black and slow-moving. Its surface reflected nothing, not even the faint glow of torchlight. It felt aware.
That was when the water moved.
A shape rose from the river, smooth and luminous, like moonlight poured into liquid form. A woman's outline took shape—long hair drifting like seaweed, eyes deep and ancient, her voice carrying the echo of tides.
Percy sucked in a breath. "A… nereid?"
She smiled at him, soft and sad. "Son of the Earthshaker."
Cynthia stiffened instantly, stepping half a pace closer to Percy without looking at him.
The nereid's gaze flicked to Cynthia—lingered. Something unreadable passed through her expression.
"You have walked far," the nereid said. "And farther still lies ahead. Your father sends aid—not victory."
She raised her hand. Three small objects shimmered into existence, resting in her palm: white pearls, glowing faintly.
"Escape, when escape is all that remains," the nereid said. "But know this—only three may return."
Percy's stomach dropped. "Only… three?"
Her voice gentled. "The sea gives, but never without cost."
She pressed the pearls into Percy's hand. Her fingers were cool, but the contact sent a jolt through him—salt and storms and something like grief.
"Your mother yet endures," the nereid added softly. "Hold to hope."
Percy barely had time to react before the water swallowed her again, leaving only ripples.
Silence crashed down.
Cynthia exhaled slowly. "That wasn't ominous at all."
Annabeth's jaw was tight. "Three pearls. Four of us."
Grover swallowed. "Let's… not think about that yet."
They moved forward.
The gates groaned open.
And Cerberus lunged.
The sound was overwhelming—three throats barking in thunderous unison, paws the size of boulders slamming into the ground. The guardian of the Underworld barreled toward them, teeth like daggers, eyes blazing red.
Grover screamed.
Annabeth froze.
Percy reached for Riptide—
"WAIT!" Cynthia shouted.
She stepped forward before Percy could stop her.
"Cynthia—!" Percy started.
She dropped to one knee.
The world narrowed.
Cerberus skidded to a halt, massive heads snapping inches from her face. Hot breath washed over her, carrying the scent of iron and ancient dust.
Slowly—carefully—Cynthia reached into her pocket and pulled out a battered red rubber ball.
Percy blinked. "You brought… a toy?"
Cynthia didn't look back. Her voice was steady, low. "Hey," she murmured, eyes locked on the middle head. "You're doing your job. That's good. You're a good boy."
The left head growled. The right snapped.
The center head hesitated.
Cynthia rolled the ball forward.
It bounced once.
Cerberus froze.
Then—chaos.
All three heads lunged—not at Cynthia, but at the ball. The massive beast tumbled, paws scrabbling, barking with pure, unfiltered joy. Stone cracked as he chased it in clumsy circles.
Grover stared. "She… she just emotionally disarmed the guardian of the Underworld."
Cynthia stood slowly, brushing dirt from her knees. "He's not evil," she said quietly. "He's lonely."
Cerberus returned, tail wagging like a wrecking ball, heads nudging Cynthia's shoulder. She laughed—an actual laugh, surprised and soft—as she scratched behind one enormous ear.
For a moment, the Underworld didn't feel like hell.
Then the shoes screamed.
Cynthia's winged sneakers jerked violently.
She gasped as her feet left the ground, body yanked backward toward the abyss beyond the gates—toward Tartarus.
"No—!" Percy lunged.
The shoes pulled harder, wings flaring, dragging her across stone. Cynthia slammed her knives into the ground, sparks flying, muscles screaming as she fought the pull.
"THE SHOES!" Annabeth shouted. "They're cursed—!"
Grover grabbed Cynthia's arm. Percy seized her other side.
The pull intensified—inhuman, relentless.
Cynthia's face twisted in pain. "They're trying—" she choked, teeth clenched, "—to take me."
Percy's heart thundered. "I'm not letting you go!"
Together, they wrenched at the laces. Annabeth's fingers flew, untying knots with desperate speed.
The ground cracked beneath Cynthia as the pull peaked—
Then—
The shoes came off.
They shot backward, vanishing into the darkness with a scream like tearing metal.
Cynthia collapsed forward into Percy's arms, shaking.
For a second, no one spoke.
Then Grover whispered, broken, "We almost lost you."
Percy tightened his grip, pulse racing. "You scared the hell out of me."
Cynthia swallowed, forcing herself upright. Her voice was rough. "Yeah. Me too."
They didn't let go of each other right away.
The palace of Hades rose before them like a wound in the earth.
Inside, shadows moved with purpose. The throne loomed—obsidian and bone. Hades sat upon it, eyes like burning coal, helm casting his face in shifting darkness.
"Children," Hades said, voice echoing. "You reek of the living."
Percy stepped forward, heart pounding. "We didn't steal the bolt."
Laughter rolled through the hall, cold and bitter. "Of course you didn't. You are pawns."
Annabeth spoke quickly, sharp and clear, laying out the logic—the timeline, the double theft, the manipulation.
Cynthia added quietly, "The bolt was meant to start a war. You gain nothing from it."
Hades studied her. Really looked.
"You," he said. "You speak like one who listens."
She met his gaze without flinching. "Facts don't care about gods' pride."
Silence fell.
Then Hades leaned back. "Very well. Bring me my Helm of Darkness. Prove my brother's treachery. Do this, and I will release what was taken."
Percy's breath caught. "My mom?"
Hades smiled thinly. "Hope is a dangerous thing, boy. Don't waste it."
They turned to leave.
Behind them, Cerberus barked—a farewell.
At the edge of the palace, Percy glanced at the pearls in his hand.
Three.
Four demigods.
The Underworld didn't care about fairness.
And the cost was coming.