Aninku and Pepicek find their mother sick one morning, and they need to buy her milk to make her better. The brother and sister go to town to make money by singing. But a hurdy-gurdy grinder, Brundibar, chases them away. They are helped by three talking animals and three hundred schoolchildren to defeat the bully. Brundibar is based on a Czech opera for children that was performed fifty-five times by the children of Terezin, a Nazi concentration camp in 1943.