The events described in the book take place on Baikal. Arthur Ronn, a resident of Yekaterinburg, has long been interested in the secrets of this mysterious place. The hero and his friends go there on vacation and disappear without a trace. His wife does not believe in Arthur's death. She returns to their vacation spot in hopes of finding her missing husband. How such a dangerous journey will end and whether it was worth going on it will become clear only at the end of this exciting story.