Mumu is the story of a rescue, the rescue of a "wretched kid" in the post-WWII years.
1947. 11-year-old Roger, a neglected, mischievous kid who excells at silly pranks, is sent to board at a small village school reigned over by Mumu, the region's nastiest teacher. He's already been expelled from several schools and this is his last chance to escape the institute for young offenders where his father has been threatening to send him. But this was without taking into account Mumu's vigilance, or how her severe demeanor hides a heart of gold.