When a scientist presents his theory that the size of the skull equates with intelligence, he is rejected by his colleagues. His theory states that Neanderthal man was equal, if not superior, to homo sapiens. After his professional rejection, the scientist is rejected by his fiancÃ©e. Mad with desire and rage, the scientist secludes himself in his laboratory where he develops a serum that turns himself into The Neanderthal Man. rumors of saber-toothed tigers roaming the countryside and several assaults on local men bring the police who attempt to solve the mystery.