During the construction of the metropolitan metro, workers uncover a precious artifact, proving that the legendary Library of Ivan the Terrible exists. Decades later, the foreman’s grandson, Ilya, stumbles upon the ancient relic in a pile of old junk. What Ilya does not realize is that the search for the lost library has been ongoing for centuries, and now powerful forces are after him. Unaware of the true value of his family heirloom, he soon learns its significance from a mysterious stranger. Together, Ilya and the stranger decide to try their luck in finding the library. They are soon joined by a beautiful philologist, Arina. The trio embarks on a dangerous quest that takes them to obscure and perilous locations across Russia, from underwater depths to the secret catacombs of the Kremlin.