That evening, Lena was supposed to be feeling calm - after all, midterms were just around the corner and most of her peers were no longer thinking about anything other than studying or relaxing. Yet she, instead of sitting over her notes, found herself on the outskirts of the city, in front of the old building that everyone knew as the 'White Lab'. At first glance it looked like a former dentist's office, closed for years after a mysterious fire. Locals still talked about the strange experiments conducted here by Dr Mandible - a mad dentist who was said to be able to fix any smile, even the most neglected. However, no one has dared to go inside since strange, shiny marks appeared on the walls and the sweet scent of mint liquid began to fill the area. Lena, curious and thirsty for excitement, could not resist the temptation. Crossing the old fence, she clutched the torch in her hand and stiffened as her shoes lightly squeaked on the decayed boards of the porch. In front of the door she saw a faded sign: 'Remember to floss! Inside, it was cool and damp. The beam of light from the torch moved over the rusting tools: drills, mirrors and even a small mouth-watering fountain, which seemed to be powered by a mysterious energy despite its years - it bubbled quietly, as if inviting her inside. Lena passed the waiting room, where educational posters from a decade ago still hung. In one, cartoon characters were battling an armada of yellow bacteria. She pulled a notepad out of her pocket: she wanted to collect material for a health film competition. Then she heard a quiet murmur, as if someone had moved deeper into the laboratory. She moved cautiously towards the closed door, from behind which came a barely audible scraping sound. Through the crack, she saw something that froze her blood in her veins: in the middle of the room stood something like a large display of toothbrushes, with small, silvery balls - apparently self-service tooth-polishing robots - circling around it. But they weren't the ones that caught her attention the most. Leaning at the table was someone in a white apron. In the torchlight, she could see his focused face and unusually white teeth, gleaming almost unnaturally. Lena bit her lip, trying not to make a sound. Then the stranger raised his head and spoke in a voice that sounded all too familiar: - I knew someone would eventually look here. You're looking for the secret of the perfect smile, aren't you? Before Lena had time to reply, she heard something start to move in the air ducts above her head. Surely it was just her and the mysterious doctor here?