Zhenka Lykov is confused: something strange is happening to his mother. In the evenings she locks herself in her room and writes in a secret notebook, telling no one anything. And one day she even disappears, leaving a note: “I went home.” The boy, his friend Olya, and the Keeper San Sanych suspect that Margarita Lykova ended up in the Dark Worlds—the realm of forgotten books, unrealized ideas, and terrible fantasies. And she could get there only through an unknown portal. To find it, the friends set off on a journey through the Book World, traveling from country to country, from era to era, searching for ancient keepers from whom you might learn something…