Frankenstein Island stars John Carradine and was the last movie directed by Jerry Warren and the only one of his low-budget films made in colour. The film opens with a hot air balloon crashing on a remote and uncharted island, the four balloonists and their dog Melvin are captured by a pair of drunken old pirates. The pirates take them to the hilltop laboratory home of Dr. Frankenstein’s modern-day descendant Sheila Frankenstein (Katherine Victor) who is carrying on the family tradition by turning shipwrecked sailors into pre-programmed bloodless, black-garbed zombies who must wear sunglasses to protect their weird white eyes from light.
Discovering that one of the new arrivals is a doctor (Robert Clarke), the buxom, white-haired Sheila quickly brainwashes him into helping her try to save her bedridden 200-year-old husband Dr. Von Helsing using the blood of a Poe-quoting prisoner (Cameron Mitchell) and the nubile bodies of a local tribe of primitive bikini-clad amazon jungle girls descended from highly advanced aliens who once used the rocky, desolate island as their secret Earth landing site.
Meanwhile, the mystic spirit of her ancestor (John Carradine) hovers ever near, channelling from the Great Beyond all the arcane energies that charge her experiments as he rants about “The Power! The Power!!”, while his immortal creation, the original Frankenstein Monster, lies trapped underwater at the bottom of a pool hidden in an underground cave, biding its time as it waits for its chance to escape.