The city of Filtronia had many secrets, but the strangest of them hid just below the surface of everyday life - exactly where the light of the lampposts reflected off hundreds of smiling faces. Three friends stood out among the inhabitants: Majka, an aspiring dentist; Kuba, a laboratory technician; and the mysterious Natalia, whose sonic toothbrush looked like a superhero's tool. One warm evening, with the scent of mint and eucalyptus in the air, something shocking happened. Cuba, getting ready for bed, discovered that one tooth was missing from his smile - it had disappeared without a trace! All he found on his pillow was a small, shiny capsule, and underneath it a note with a message: "The tooth has been taken by the Hooded Stone. Only those who know the secrets of brushing can get it back." Majka and Natalia appeared immediately. In Kuba's laboratory, where mouthwash was bubbling in forestry tubes, a feverish investigation began. The friends analysed the capsule and, under the microscope, discovered a micro-sign: a miniature map leading to the abandoned Candy Passage under the Old Dental Clinic. There, between worlds of paste, threadlike portals and bacterial colonies, they were about to embark on a mission to retrieve a tooth and clash with the Hooded Stone. However, as soon as they opened the latch on the underground passage, they heard a quiet rustling.... Who else lurked in the darkness of the damp corridors? Would they dare to go deeper, not knowing what waited around the corner?