Summer holidays have always been magical. Perhaps because they idealize the memory of adults at the time of the greatest possible freedom: no school, no work, but room for a lot of new experiences, adventure, and first romances. Whether in the world of Astrid Lindgren, which seems to be always set in summer vacation, or in somewhat rougher renditions such as "Stand by Me," a single summer can define one's whole life. The tenth summer of Kalli is certainly one of these magical experiences. Along with his friends, he initially planned great things, including opening a zoo - however, one that not only offers the ordinary creeping or fluttering items in a preserving jar, but a true sensation. And suddenly there appears a little monkey, from dubious origins. But where to keep it? Kalli has an idea and his thoughts turn to his mysterious neighbors. The strange neighbor Mrs. Hilfers and her daughters, who have earned both an extremely wicked reputation and also a surprisingly warm reaction ...