"We should go back," Usopp whispered, peering nervously over a moss-covered wall.
Chopper shivered beside him. "But what if it's important? Robin said ancient symbols usually mean something!"
Before them stood the sealed gate they'd found the night before. Faded sigils still marked the stones—a mixture of swirls and lines that hummed faintly in the afternoon sun. The door hadn't been opened in decades, maybe centuries, but something behind it pulsed faintly. Alive.
"We just tell the others and let them mess with cursed doors," Usopp muttered.
But curiosity won. It always did.
Chopper bent down and studied the largest sigil. "It looks like an old Marine cipher, but... weirder. Like someone changed it."
"Changed?"
"Yeah. To lock something in. Or maybe out."
A soft tremor rumbled beneath them.
"OKAY TIME TO GO," Usopp yelped, grabbing Chopper. But the little reindeer stood his ground.
"Wait! There's a vent shaft! We can see what's inside."
The two crept around the ruined stonework and squeezed through a narrow, mossy channel until they reached a broken opening—a hole just wide enough for a pair of small adventurers.
What they saw inside made their stomachs drop.
A massive stone hall, lit by cold blue lanterns, stretched beneath the town. Machinery hummed at its edges. In the center stood a monolithic stone emblem—part World Government, part something older, darker. Rows of covered capsules lined the far wall. Inside some, faint silhouettes rested.
"Are those... people?" Usopp whispered.
"Experiments," Chopper said grimly. "Or prisoners."
Another tremor. This time louder.
They backed away.
"We have to tell Robin," Chopper said, trembling.
Usopp nodded quickly. "Yes! Agreed! Let's get out of here before one of those capsules opens up."
As they turned to crawl back, a soft metallic clink echoed from the shadows behind the sigil wall. Neither looked back.
Back at the Sunny, Robin stared at a dusty volume she'd uncovered from the town archives. Its cover bore the same sigil Chopper described.
"This place... it's built over a failed Marine science post," she said.
Franky raised a brow. "Vegapunk stuff?"
Robin shook her head. "Older. Prototype weapons research. They were trying to combine Void Century tech with modern science."
Zoro scowled. "That sounds like a great reason to burn it down."
"They never did," Robin said. "They buried it."
Nami stepped in, arms folded. "We need to move fast. If Kael knows about this, he might not be here for us. He might be here for that."
Luffy scratched his head. "So the town's standing on top of a big spooky hole?"
Robin gave a wry smile. "Essentially."
Brook floated into the room, his usual cheer dulled. "There's something else. I asked around town. The locals know. They're just scared. No one builds basements here. No one digs. Ever."
Franky frowned. "That explains the weird plumbing."
"Or why some buildings feel... tilted," Chopper added as he and Usopp stumbled back into the room.
They relayed what they saw. The hall. The capsules. The emblem.
Robin grew still.
"I know that emblem," she said. "It was part of a secret initiative: Project Helix. Discontinued after Enies Lobby. It was deemed too unstable."
Zoro leaned against the mast. "Then why is it still down there?"
"Because the World Government doesn't destroy its sins. It buries them."
That night, Kael stood alone in the ruins outside the temple wall. The air pulsed softly around him. He ran a hand across a sigil.
"She died to protect this secret," he whispered.
Behind him, a cloaked figure emerged.
"And now the Straw Hats know."
Kael didn't move. "Let them. If they open that door, they deserve to see what's inside."
His fingers clenched. His eyes burned.
"But if they get too close to what killed Noel... I will stop them."