Maja was fourteen years old, a skateboarder, and an unusual talent for asking questions. In her school oral hygiene circle, everyone knew her persistence and curiosity. One morning she found a package in her mailbox with a white toothbrush signed Whisperer. When she touched the fibres, the toothbrush trembled and she quietly hissed: "From today I will guide you." Maja laughed, thinking it was a joke from Kuba in their class. At the assembly, the headmaster announced Smile Week and a competition for the best school poster. Then he showed old plans of the basement under the gymnasium, with the water pipe maze marked. The whisperer began to tremble like a mobile phone in Maja's hand and whispered only: "The acid is rising." Maja used the pH test strips at the school tap and turned pale. The water had a reaction that favoured the poster and the taps smelled sticky sweet. After school, she gathered up Cuba and Lena, and the kit: mirrors, floss, UV torches. In the bathroom, they outlined a plan and refreshed their smiles, brushing their teeth for two minutes. Maja repeated the circular motions, then the floss between the teeth, and finally the fluoride liquid. This was their ritual and code: morning and evening, thoroughly, unhurriedly. Under the UV light, the tiles trembled blue, showing traces of sugar haze. The trail led to the service mirror, behind which a grille and cool pipes buzzed. Lena unhooked the grating, using the thread like a rope, while Cuba held the torch. They squeezed into the technical tunnel, where a 1989 poster hung: 'Fluoride protects enamel'. It echoed like silent chewing, and sweet crystals spilled from the walls. At the end of the corridor, a textured enamel door had a rotating molar embossed on it. Maja applied the Whisperer and made slow circles until the lock began to resonate. A warm breath gushed from within, smelling of bubble gum and anxiety. The toothbrush sang thinly: "Get the fluoride rinse ready, this will come in handy soon." The door sprang open, revealing something that shimmered like a toothstone but moved. Kuba squeezed the bottle of liquid, Lena picked up the floss, and Maja took the first step.