In psychedelic swinging 60s style, the dreaded thief (and killer) Diabolik wreaks havoc on a generic European country for his own financial gain and amusement. He shares an extravagant underground lair (and a giant bed of money) with his curvaceous, superficial girlfriend...who uses her awesome powers of wig-wearing to help Diabolik kill innocent people and steal billions from the government. Nonetheless, Diabolik is the "hero" of the film because he must face off against bumbling cops and revenge-seeking mafiosos.
