Cambrian - the oldest geological formation, petrified sea - should give oil! The hero of the book, young Vasily Zyryanov, together with his comrades and voluntary assistants, conducts exploration of Siberian oil. As a teenager, Zyryanov worked as a pilot on the northern rivers, now he has become a prospector of the Cambrian Sea, whose oil is so needed by the five-year plan. The action of Fyodor Pudalov's novel takes place in the 1930s, but among the heroes there are people who do not know what is happening in Russia. These are residents of the ancient settlement of Russian people lost in the taiga. One of them, Nikolai Ivanovich Menshik, unexpectedly falls into a new, Soviet century. A whole layer of life of Russian settlers in Siberia, also a kind of "Cambrian," reveals the author of the novel. The ancient features of everyday life, the flexible and expressive language of our ancestors coexist in the book with the life and speech of contemporaries.