Twelve year old Jan Grovers spends more time in the alleys of Rotterdam than with his family (though he occasionally looks after his tree younger sisters, all of whom are called Mientje). Together with his best friend and partner in crime Pietje Puk he plans to travel to America to get rich. When a local clergyman takes pity on the boy and tries to teach him good manners, Boefje at first rebels. However, once he is sent to a strict boarding school, he takes an interest in music, specifically the pipe organ.