Aninku and Pepicek are a fatherless sister and brother. Their mother is ill, and the doctor tells them she needs milk to recover. But they have no money. They decide to sing in the marketplace, to raise the needed money. But the evil organ grinder Brundibar chases them away. However, with the help of a fearless sparrow, keen cat, and wise dog, and the children of the town, they are able to chase Brundibar away in turn, and sing in the market square.