The film takes place in a small village named "Malevil" within central France. Due to an administrative issue, the mayor, pharmacist, farmers, traders, and other villagers attend a meeting in the local château's large wine cellar on a beautiful sunny day in late summer. However, while the meeting is taking place the radio suddenly cuts out. Moments later, huge explosions occur followed by long and violent flashes. The noise, excessive heat, and moisture cause everyone in the cellar to fall unconscious. The survivors awaken to find a scorched world where almost nothing remains. They embark on a new life faced with isolationism and violence. It is based on the 1972 science fiction novel of the same name by Robert Merle.

References:
https://en.wikipedia.org/wiki/Malevil_(film)