The night was quiet, all the way suspiciously quiet, as Adam and Lena crept up to the fence of the Smile Institute laboratory. No one believed the school rumours about the secrets hidden inside, but Adam loved a challenge, and Lena she just couldn't say no. It was going to be a simple bet: 'We'll go inside, have a look around and take a selfie at the weird toothpaste machine,' Adam promised, and Lena - though not convinced - agreed. They snuck out of the house shortly after twenty-three. Getting through the fence was child's play, and locking the front door was downright ridiculously easy to break through with a lock pick Adam had found at an antique market. The interior of the laboratory turned out to be much more interesting than they had thought: a barely perceptible smell of mint wafted over the sterile worktops, and reflections of light from hundreds of shiny instruments danced across the walls. On one of the tables lay a thick book with the inscription 'DNA of caries bacteria - experimental report'. Lena glanced at Adam, raising an eyebrow. 'Do you think they can really create a bacteria that.... cleans teeth? - she whispered. Adam shrugged his shoulders. 'We're about to find out. They moved on to the next room. Here they noticed something strange: a shadow flickered through the glass of the door to the cold room, as if someone was moving around in there. At the same time, the lights in the laboratory suddenly dimmed and a cool computerised voice came from the speakers: 'Please leave the research area immediately. The purification procedure will be activated.' Adam stuck his back to the wall. Lena pulled out her phone, but the battery died in the same second. A strange, rustling-like sound came from the cold room, and a shadow began to slowly approach the door. Something about its silhouette didn't seem to match a human being.... and then pulsating blue lights came on from the depths of the laboratory, and the whole building shook from a quiet, mechanical buzzing. Adam looked at Lena with wide eyes. They had to make a decision - stay and see who or what the mysterious shadow was, or find an escape route through the unfamiliar corridors of the Smile Institute. Every second could have been decisive....