Boris Karloff ranks among cinema history’s most iconic and revered horror stars and creature performers, responsible for some of the most unforgettable monsters ever brought to the screen. Frankenstein’s Monster and The Mummy are, of course, key examples, yet Karloff appeared in a staggering 1,974 films over his nearly five-decade-long career. His roles spanned from a bit part in the 1919 serial Lightning Rider to his final American film, Peter Bogdanovich’s 1968 thriller Targets, a standout work.
Though Karloff is widely celebrated for his impressive emotional range and striking intensity, one of his finest films remains regrettably overshadowed by his more high-profile projects. It’s time to revisit the legacy of 1936’s notably underappreciated Universal picture, The Invisible Ray.
The film follows astronomer Dr. Janos Rukh (Karloff), who has created a telescope said to peer so far into deep space’s light rays that it can offer a view into Earth’s past. He invites skeptical colleagues—Dr. Benet (Bela Lugosi), Sir Francis Stevens (Walter Kingsford) and his wife Lady Arabella (Beulah Bondi)—along with her nephew Ronald Drake (Frank Lawton) to observe his test of the telescope and the device capable of “reading” the data encoded in those light rays. The test succeeds, prompting Dr. Benet and Sir Francis Stevens to invite Dr. Rukh on an expedition where they uncover an ancient meteorite. Rukh is exposed to its unknown radiation, dubbed “Radium X,” which makes him glow and grants him a lethal, destructive touch.
Dr. Benet creates a serum that slows the radiation’s toxic impact, yet the exposure still warps Rukh’s psyche. He learns that Dr. Benet and Sir Stevens have taken a meteorite sample to an international conference to prevent its monopolization, and that his wife Diana (Frances Drake) has left with Ronald. Driven insane by the radiation, he embarks on a revenge mission to kill the expedition members, with a suspicious Dr. Benet close on his trail.
Though Karloff remains best known for his masterful depictions of some of cinema’s most enduring monsters, his turn as Dr. Rukh deserves a place in that discussion. In the film, he transitions from a bitter scientist to a heartbroken husband, then to a fixated killer, anchoring the role with unexpected depth despite the requirement to glow in the dark. Karloff’s dialogue delivery is exceptional here (“I could kill a nation, all nations,” he remarks, reflecting on his new powers), and the film stands out for its genuinely tragic ending, where the person Rukh loved most is the one who brings about his downfall.
The Invisible Ray holds a distinct spot in film history for several reasons. Following Karloff and Lugosi’s rise to national stardom via Frankenstein, Dracula, and other monster classics, Universal paired the two in three additional films: the horror-comedy The Black Cat (1934), the Poe-inspired The Raven, and The Invisible Ray. As their final collaboration among the three, Ray marks a milestone in their storied careers, and their on-screen chemistry is exceptional. As Rukh grows more menacing in his killing spree, Bela Lugosi’s Dr. Benet infuses the role with intelligence and understated empathy, creating strong interplay between the two.
The 1936 film also stands as a pioneering sci-fi spectacle within a notable and influential lineage. Anxiety about radiation’s destructive potential inspired numerous 1950s films, including American titles like Them! (1954), Creature with the Atom Brain (1955), and The Amazing Colossal Man (1957), as well as Hammer Horror’s X the Unknown (1956), or (1954). The Invisible Ray, however, can credibly claim to be the first sci-fi horror film to use lethal radioactive mutations as a plot device (even if the science is notably shaky and the radiation itself is fictional). It’s a true landmark in what would evolve into a hugely influential subgenre, arriving nearly two decades before its time.
For all these reasons, The Invisible Ray deserves to be revisited and remembered as the classic it is. While the African expedition includes problematic colonialist undertones, a clear product of its time, the film remains a significant part of cinematic history. Karloff delivers another stellar creature performance, with more room to emote thanks to an effects-driven, makeup-free role. It’s a terrific collaboration with Lugosi, a monumental entry in the radioactive horror subgenre, and an engaging revenge tale to boot. Ninety years later, it’s long overdue to recognize just how excellent it truly is.