An unknown weed is rapidly entwining the Earth with its tentacles. People who find themselves near the plant go crazy. The Thicket itself generates terrible monsters created from the living organisms it kills. Suddenly, it turns out that only people with Down syndrome can resist the destructive nature of the weed. The Institute of Cosmic Infections gathers a group of travelers for a trip to the center of the parasitic plant. Among them, Kostya is especially distinguished. It is he who will have to get to the central root and inject a chemical that can destroy the Thicket. Only at the end of his journey Kostya learns something that will change the life of mankind forever...