Valley of Four Crosses. The Legend of the “Earth People”. Riddles of Khairkhan. Tales of brotherhood. “Find and don’t give up.” Aspiring to the sky. First confession. Kara-Serdar. Based on a purely fantastic assumption – the possibility of creating a chronoscope, an electronic machine that reproduces events of the distant past, I. Zabelin talks about adventures that took place at different times. The fate of the disappeared polar expedition, the solution to the legend of the “earth people”, the secrets of the Khairkhan cave and other historical, geological, archaeological mysteries – this is the content of the stories. The convincing style of the story is given by the realistic style of writing: the action takes place in a modern setting, its heroes are participants in geographical expeditions.