It's summer. Kalle, Eva-Lotta and Anders have formed a gang, the White Rose. They are in playful battle with Red Rose gang. A relative of Eva-Lotta's mother, Uncle Einar, come to visit and Kalle notice immediately that he is behaving strangely. Einar seems to have hidden something in a closed mine outside town. Two mysterious strangers appear.

Kalle Blomkvist
Anders Bengtsson
Eva-Lotta Lisander
Sixten
Benka
Jonte
Uncle Einar
Constable Björk
Fredrik med foten
Detective Inspector Stenberg at the State Police
Tore Krok, alias Arthur Berg
Ingvar Redig, alias Tjommen