There are moments that change the course of history, dividing life into “before” and “after”. And often those who take the decisive step cannot even imagine what their actions will lead to... Twins Dimka, Vitya and Nastya grew up in Spasgorod - a huge steel tower that reliably protects residents from the dangers of the outside world. Like other children, they went to school, tried not to upset their parents and obey the rules of the Overseers - a mysterious organization that controls the lives of people and Lifts. But one day the twins found a strange door. And they remembered: each of them saw exactly the same one in a dream. The fate of the city changed the moment the guys decided to find out what was behind it...