Meteorologist Jan Becker has lived in America for a long time to study tornadoes and suspects something terrible when he returns: the extreme weather conditions in Germany - heat and hailstorms in a confined space - have the potential to spawn a huge tornado. But no one believes him, especially not his father, the head of the weather service. When a supercell forms a short time later in the Berlin area, Jan immediately sets off to gather evidence for his theory.