Berry is fourteen years old and freshly fitted with braces. She tried to pretend that nothing had changed, but the wires buzzed with every laugh. After dinner she would spend two minutes brushing, a minute flossing, and still rinse with fluoride liquid. That evening, she added an experiment: a drop of plaque-staining liquid to see where she was really failing. In the mirror, she saw blue-purple marks arranged in the shape of a key on her lower molar. - Really? - she mumbled and zoomed in on the UV lamp from her biology kit. The fluorescence flashed not only on the tooth, but also on the mirror, right next to the handle. Where she wiped with a towel, three small tooth outlines appeared, like road signs. She called Maks, who was making a film about daily oral hygiene for a competition. They made an appointment outside the school because the bathroom had big mirrors and old pipes, smelling of mint. In the evening twilight, the school corridor sounded like the inside of an empty shell. Maks held a tripod and chewed sugar-free gum to help him focus. - 'Two minutes, circular motions, no rush,' he repeated like a voiceover as they entered the bathroom. Berry poured a drop of staining over the mirror and then illuminated it with a violet lamp. An inscription appeared on the surface: Don't stop brushing, or you'll wake Stone. Below the inscription, an arrow-shaped foam spilled out, pointing straight towards the dentist's office. The office was seemingly closed for renovations, but the door gave way after a slight push. An armchair waited like a stage chair, with a blue polka dot bib dangling by it. Berry grunted, corrected the placement of her lips on the camera and switched on the lamp. The sink shone with letters like tooth roots, and the mammal trembled as if someone was whispering through the water. - Can you hear it? - asked Maks, pulling dental floss from his pocket like a lifeline. A new sentence flashed on the porcelain, shorter and sharper: The two-minute guard is waiting. Something clicked in the tool cabinet and the handle behind them dropped.