In a small village in 1949, Thomas, Renate and Ernst found a "Federation of Justice." Like their hero, pirate Klaus Störtebeker, they steal from the rich to give to the poor. The adults don't seem their well-intentioned projects in quite the same light, and Thomas and Renate decide to join the new Pioneers organization instead. Ernst is disappointed and continues dishing out justice on his own.
The Pioneers learn from village records that the fields which rich farmer Mehrin has taken for his own use are actually town property and decide they should build a playground there instead. When the playground burns down overnight, Ernst joins the Pioneers in searching for the person responsible.