Years ago, Lepel's parents left an hot air balloon world tour. He stays with granny Koppenol, who constantly exploits him for domestic chores, in her buttons shop and even as accomplice in the department store where she steals the buttons from clothes. After she won't even leave him the balloon kind salesman Max gave him, Lepel, now 9, runs away. He meets Max's slightly older daughter Pleun. Schoolmaster Bijts is also looking for him, but only as arithmetics talent for an academic schools contest. Max accidentally finds out the sad truth about Lepel's family.