New teacher Heider takes up his post with great enthusiasm. His unconventional ideas meet with incomprehension and mistrust from the old head teacher Ruppert. When a boy has an accident on a school trip, the children blame Heider. The parents turn against him and he is suspended from his job. But Ruppert has come to respect the new boy. He does not believe he is to blame. Meanwhile, the children are preparing the next mischief. They want to blow up a ruin with explosives found in the forest. Heider is able to prevent this at the last minute. He is rehabilitated and everyone happily awaits his return to school.