Lena had had enough of this school year. Her last biology project seemed worse than her matriculation preparations. Together with her friends Igor and Marta, they had been 'luckily' selected for the most boring experiment: for one week they were to document the effects of different toothpastes on dental models. The dental laboratory at their high school, usually lit by sterile light and full of the smell of menthol, seemed different this time. The shadow falling through the milky window was arranged in strange shapes, and the metal tools cast frightening blips on the walls. On the table were three jaw models resembling frankly smiling masks, and in the middle - a mysterious test tube with an unmarked paste that even the teacher spoke of in half whispers. - What if this paste is not allowed? - asked Marta, looking at the package with the label written in Latin. Igor just shrugged his shoulders. - 'Maybe it's some outdated sample, don't bother. So they set to work, trying to ignore the strange atmosphere. However, after just a moment, Lena felt that something was wrong - the small model of the front teeth, which had been clean a moment before, was covered in a fine blue tarnish. When she tried to brush it, the plaque would not come off. Igor looked at her with irony: - I think we gave too much toothpaste. But Marta did not respond. She stood as if hypnotised, staring at the microscope screen. Lena approached and saw reddened, almost fluorescent tissue - something she had never seen in textbooks. At the same time, the lights in the lab began to flash. Someone hooked the door - it was locked. - Does anyone else smell... menthol? - whispered Lena as the air grew cool. Suddenly there was movement among the models. One of the plastic molars moved slightly, as if something had started to hatch from it....