Night had fallen over the city. Olivia, a newly minted dentist, sat alone in her office after hours. The strange thing was that for 24 hours no one had come in with a toothache or even for dental floss. As she was gathering herself to leave, she suddenly heard a quiet knocking. The door to the small bathroom opened slowly, although she was sure she had locked it. A small, shimmering creature slid out from inside - it measured maybe fifteen centimetres tall, had hair like white threads and was dressed in a garment of soft sponge. The creature smiled broadly, displaying a row of tiny, perfectly white teeth. - Olivia, you have to help us,' she whispered. - 'We are brush elves. We live beneath the surface of the city. Something bad has been happening for a week: dark stains are appearing on the houses and our friends are disappearing without a trace.... Olivia felt her heart start to beat faster. Before she could say anything, the elf opened a secret hatch in the floor and invited her inside. Where the ground should have been, a network of luminous corridors appeared. Stepping through the underground city of teeth, Olivia saw miniature houses shaped like molars, fountains rinsing with mouthwash, and the smell of mint in the air. Everywhere, however, there were signs of distress: patches of decay slowly covered some of the houses, and the inhabitants looked at Olivia with hope and fear. - 'Come, you must see King Pastelon's throne,' whispered the elf. - Only he knows the secret recipe for the paste that can save our city. As they entered the darkest corridor, a growing murmur came from around the corner.... someone or something was waiting there in the darkness.