International man of mystery Diabolik and his sensuous lover Eva Kant pull off heist after heist, all while European cops led by Inspector Ginko and envious mobsters led by Ralph Valmont are closing in on them.
Two traffic policemen help capture a dangerous robber after unwittingly contributing to his making off with the loot.
Ottone and Savio work hard to keep each other out of trouble with the Roman Centurions while scraping together food and drink with various scams. Emperor Nero's wife, the beautiful Poppea, takes an interest in Ottone, who after a short stint as a gladiator gets a region to manage and an army of his own to command, all the while assisted by his best friend and partner in crime Savio.
