Using his marauding robot and other futuristic weapons, power-crazed scientist Professor Ravello carries out various plots to win the hand of Evelyn away from her true love Harry Peel.

A black envelope presents the hero, detective Harry Peel, who loses his fortune over the course of the story, with tasks. A mysterious criminal, car and motorcycle chases through the wintry Alps, and the blowing up of a bridge provide cinematic spectacle and opportunities for daredevil stunts.

The industrialist's daughter has been kidnapped by the mad inventor Ravello, but Harry Peel stays hot on their trail with the help of his dog Greif. Behind a waterfall, he discovers the hidden gate to Ravello's castle, where the fiercest of battles now break out between the two and Harry finds himself confronted with a staircase that has been electrified and, once again, with the deadly robot.