Zhen’ka woke up in a cold sweat: in a dream, he saw an unfamiliar room filled with shelves of ancient tomes. Suddenly, in the room a terrible green substance appeared and began greedily, with slurping sounds, to consume everything around it. Ugh, what a nightmare! In the morning the boy forgot about the horror. And he probably would never have remembered it if, during his vacation in the countryside, he hadn’t heard how his “progress-deprived” grandfather was talking on Skype about the appearance of some intelligent green slime threatening the life of an entire world…