Dracula vs. Frankenstein (1971)

Judith Fontaine is looking for her sister Joanie, who has disappeared into the hippie community of Venice, California. It turns out that Joanie has become fallen victim to Groton, an axe-wielding homicidal maniac under the employ of Dr. Durea, the last living descendant of the Frankenstein family and is now both running a house of horrors on the beach's boardwalk and performing experiments on Groton's victims in his basement laboratory.