Erwin Strahl

Both Scotland Yard and an amateur American sleuth are tracking a master criminal known as The Frog. This moniker refers to the bulging-eyed mask worn by the evildoer, and is reflected by the frog icons painfully tatooed onto the forearms of his henchmen. The trail leads to the country manor of an enigmatic, steely-eyed nabob, whose repressed son has eyes for the artistes at the Lolita cabaret, and whose lovely daughter captures the fancy of both the American playboy and the villain himself. (imdb)

A new international terrorist group attack the castle of an Austrian prince during his party, but one of the guests, a CIA contractor, deals with them. The CIA hires him to find the men behind the attack and take them out.