In Lillköping, the exciting war between the Red and White Roses continues. One night, when the White Rose wants to win back the coveted Big Mummrich, they witness how the professor and his little son Rasmus are kidnapped by unknown men. Eva manages to hide in the kidnappers' car and with the help of various leads she lays, Kalle and Anders find her in the villains' headquarters. As it turns out, the professor invented an indestructible light metal and the head of the kidnapping gang spared no means to get hold of the formula. It's a pretty tricky situation, but luckily there's Kalle Blomquist...