Frontier Hellcat was the fourth in a series of 1960s European westerns based on Karl May's "Winnetou" character. Stewart Granger takes over from Lex Barker in the leading "Anglo"-role of the mysterious maverick who wanders from town to town doing the "Lone Ranger" bit. The hellcat of the title is Elke Sommer, a tempestuous frontierswoman who reluctantly accepts Granger's help in attaining safe passage through the Rocky Mountains ("played" in this film by the Alps). The original title of Frontier Hellcat was Unter Geiern; the production was a cooperative effort, with contributions from West Germany, France, Italy, and Yugoslavia. Stewart Granger would star in the "Winnetou" saga again in Rampage at Apache Wells and Old Surehand.