Maria and Frieda, recently orphaned identical twin teenage girls, move from Venice to Karnstein in Central Europe to live with their uncle Gustav Weil. Weil is a stern puritan and leader of the fanatical witch-hunting 'Brotherhood'. Both twins resent their uncle's sternness and evil twin, Frieda, looks for a way to escape. Resenting her uncle, she becomes fascinated by the local Count Karnstein, who has the reputation of being "a wicked man".