Elderly, impoverished professor Dr. Marcus Monserrat (Boris Karloff) promises to painlessly cure stammering, self consciousness, anxiety and other psychological problems through "medical hypnosis." He and his wife/assistant Estelle (Catherine Lacey) run a small clinic out of their own home where they treat patients, but are actually looking for a guinea pig in their mind-control experiments as young antiquity store owner Michael (Ian Ogilvy) soon finds out. While hanging out in a cafe, Michael is approached by Marcus, who promises "an extraordinary evening" if he'll simply follow him home. Michael, who's looking for some excitement and getting a bit bored hanging out in swingin' London clubs with his mechanic best friend Alan (Victor Henry) and sort-of girlfriend Nicole (Elizabeth Ercy), takes him up on the offer, allows the professor to hook him up to a machine, some psychedelic swirls are projected onto his face and now the professor and his wife can control his every action. Not only that, they can also feel exactly what he feels.
Though Marcus wants to immediately share his discovery with the scientific community so it can be used for good, Estelle talks him out of it. She wants vindication for him having been laughed at and discredited by his peers 30 years earlier, which effectively ended his professional career and caused them financial hardship ever since. Estelle first uses their hold over Michael to make him break into a store and steal a fur coat. She then wants to feel the exhilaration of speeding across the country on a motorcycle and the adrenaline rush associated with physical violence. The more she experiences, the more power-mad she becomes. Estelle incapacitates her already frail husband, destroys his equipment and eventually forces Michael to stab his ex-girlfriend (Susan George) to death with a pair of scissors and strangle a pop singer (Dani Sheridan). Michael's chums begin to realize something's not quite right and the cops (led by Ivor Dean) start to close in on him.
I'm not quite sure what the "point" of this might be, but the storyline itself is full of subtext that helps to keep things interesting. We have an older couple controlling and living vicariously through a young host; experiencing the thrills and highs of a liberated, carefree youth that they likely never had a chance to experience in their own lifetime. As compromise, any time Michael experiences pain or injury, it's also felt by Marcus and Estelle. We also have the power play between husband and wife. From all indications, Estelle has been a supportive, subservient housewife for many years, always cooking her husband dinner and dilligently assisting him in his experiments. The very moment she gets a little control, she uses her newfound freedom to lash out, get the upper hand on her husband and enact out her own little violent scenarios.
Though the film certainly falls short of its true potential, often seems unfocused and spends too much time showcasing lame pop acts at the nightclub (likely to appeal to a younger audience), this still has its merits. Especially noteworthy are the two lead performances; Karloff does a fine job engaging our sympathies, and he's matched every step of the way by Lacey in the showier role as the increasingly unhinged wife.
Director Reeves had previously made THE SHE-BEAST (1965), went on to his greatest glory a year after this one with WITCHFINDER GENERAL (1968) and died of an "accidental barbituate overdose" in 1969 right before production was to begin on THE OBLONG BOX (1969), a project that was handed over to director Gordon Hessler. He was just twenty-five years old. Production company Tigon Film Distributors also released CASTLE OF THE LIVING DEAD (1964), which was co-written by Reeves, who also served as second unit director on the film.
Allied Artists handled theatrical distribution here in the U.S., though it's never been officially released here on DVD.