A dental student, a biologist, and a biotech specialist stumble into an underground kingdom hidden inside a colossal set of teeth, where the locals fear toothbrushes and something in the dark is waking up.
Marta had just sealed the last vial of nanorobots when Bartek called, his voice thin with excitement and something closer to fear.
"You need to come to the Whispering Cave," he said. "Now. We found something that should not exist."
An hour later, Marta and Kaja were following him through a narrow crack in the mountains, their headlamps cutting pale arcs across the stone. The passage narrowed, dipped, and then opened into a tunnel so smooth it stole the breath from Marta's lungs. The walls were white, faintly glossy, and curved in a way rock should never curve.
Kaja ran her fingers over the surface and pulled back at once. "This isn't limestone."
Bartek swallowed. "I know."
They moved deeper. The tunnel branched again and again, all of it gleaming in the same strange enamel sheen, as if they were walking through the inside of a giant mouth frozen in stone. Marta's pulse ticked faster with every step. The air even smelled wrong: cold, mineral, and faintly metallic, with an edge of something sharp and clean, like antiseptic left too long in a closed room.
Then came a sound from ahead. Not footsteps. A soft, delighted giggle.
Three figures stepped out of the dark, each a little shorter than Marta, dressed in grey aprons, their heads shaped like toothbrush bristles and their smiles unnervingly wide. Behind them, more pairs of eyes blinked open one by one in the shadowed corridor.
The oldest of the trio lifted a hand. "Welcome to Molarion," it said. "You may stay, if you help us. We have a hygiene problem we cannot solve ourselves. And you must not, under any circumstances, use toothbrushes."
Before Marta could ask why, a green light flared deep in the tunnel. Something answered from far below with a long, dragging sound, like thousands of tiny bristles scraping across bone. The floor shuddered under her boots. Kaja took a step back. Bartek stared past the creatures, his face gone white.
From the darkness behind them, something began to move faster.