A fascinating story about the adventures of a fifth-grader Fedya Kuznetsov, who penetrated into the world of little people - Hermites, the mysterious inhabitants of St. Petersburg palaces and museums, invisibly existing in the city since its foundation. Fedya finds himself in a whirlwind of events related to the hidden life of St. Petersburg, and takes part in the fight against the insidious snake that escaped from the Bronze Horseman. If the dark forces win, there will never be white nights in St. Petersburg again. Fedya helps the Hermits defeat the snake and restore order in the city.