Whilst enjoying his holiday in a Tyrolean village, artist Paul Greville encounters the young and beautiful Helen, a waif-like siren who roams the woods alone, possessing a scar in the form of a spider on her shoulder. Back at the inn, Paul finds trouble in the form of innkeeper Johanne, together with his seductive daughter Anna, whom seduce and exploit Paul's affable nature. When Paul is attacked by Johanne's thugs, the inn-keeper winds up dead, sparking a man-hunt by Anna who becomes desperate for revenge. Now on the run, Helen takes Paul to her father's cottage, where a diabolical series of experiments is being conducted which involve animals. Using money from stolen paintings to finance his fiendish scientific dabblings, Paul is again placed in a procarious position involving Helen's father, who is desperately trying to create a deadly nerve gas - but not before Anna's henchmen, hot on their heels, close in for the film's terrifyingly 'explosive' confrontation.