During the construction of the metropolitan metro, workers discover a precious salary, which proves that the legendary Library of Ivan the Terrible exists. But the find turns out to be forgotten for many years, and already in our time it falls into the hands of the unsuspecting Ilya. Now his life is in danger, because powerful forces are hunting for an ancient artifact. The guy is forced to team up with a stranger who claims that the salary is the key to finding the Library. To help them in their search and unravel the ancient ciphers, the beauty-philologist Arina is taken. Now, in order to find new clues and get closer to the solution, the trio of adventurers need to visit the lost and dangerous places scattered throughout Russia: from Vologda to Naryan-Mar, on land, under water and even in the secret dungeons of the Kremlin.