For several generations, people have lived in an underground city illuminated only by lanterns. The city's creators calculated that the inhabitants would be able to reach the surface after 200 years, and left instructions sealed in a time capsule. The capsule was kept and passed from one city mayor to the next. However, due to circumstances, this chain was broken, and the box with the instructions was lost. Two hundred years have long passed; food supplies are running low, and the heart of the underground city—the power generator—has exhausted its service life and is functioning, literally, on a word of honor; but it does not see this as a big problem... for itself and does not intend to seek a way to save the other inhabitants. The forgotten instructions are accidentally found by Lina, and now she, together with her friend Dun, are trying to decipher the message, overcome people's distrust, fear, avoid traps, evade police pursuit, and help the residents of the fading city find a path to a new world.