In an ancient castle overlooking a small village in Mexico lives Maria Frankenstein (Narda Onyx) and her brother, Rudolph (Steven Geray), the grandchildren of the infamous Dr. Frankenstein, whose monster creation horrified Europe fifty years ago. As Jesse James (John Lupton) and his friend Hank Tracy (Cal Bolder), the last of the James gang, ran from an American posse; Hank is wounded. They meet Juanita Lopez (Estelita Rodriguez) in the village, and she takes them to the village’s only doctor. Once there, Maria sees this as a chance to complete her grandfather’s work. She sends Jesse and Juanita to get medicine for Hank and, while they are gone, performs a brain transplant on Hank and names the result Igor.