Lambert Hillyer’s The Invisible Ray isn’t related in any way to Universal’s Invisible Man series (no-one actually becomes invisible for starters). Instead, it’s a slightly odd beast that starts out in tried-and-trusted Gothic territory, takes a detour into African adventure rom/science fiction and ends in mad-killer-on-the-prowl territory. It was made a troublesome time for Universal, with rumblings of the studio being sold off, and replaced an abandoned version of Bluebeard that was, like The Invisible Ray, meant to be the second pairing of Boris Karloff and Bela Lugosi.

The first act is pure Gothic, full of raging storms, dire warnings from an old woman (Rukh’s mother, played by Violet Kemble Cooper) and a fine old castle “on top of the Carpathian mountains.” Here; astronomer and inventor Dr Janos Rukh (Karloff) has built a telescope that can look deep into the universe and capture images of light rays that show the Earth’s past. Widely discredited by sceptical colleagues, he arranges a demonstration at his observatory for two of his most vocal detractors, Dr Felix Benet (Bela Lugosi) and Sir Francis Stevens (Walter Kingsford). They’re astonished when Rukh shows them images of a meteorite crashing to Earth a billion years ago somewhere in Africa. Won over by the demonstration, the pair invite Rukh to join them on expedition to find the impact site and in the second act, we leave behind the stormy, windswept Carpathians for a sweltering Africa.

Once there, Rukh quickly finds the remains of the meteorite, but is exposed to “Radium X”, a hitherto undiscovered form of radiation that causes him to glow in the dark (like one of those Aurora monster model kits of later decades – had the film made more of an impact on the public, Rukh would have been a shoe in for one of the models) and make his touch deadly to anyone it comes into contact with. Benet develops a serum that contains the spread of the toxicity, but Rukh driven mad both by the Radium X and by the discovery that his wife Diana (Frances Drake) has fallen for Ronald Drake (Frank Lawton), the nephew of Stevens’ wife, Lady Arabella Stevens (Beulah Bondi). Rukh retreats to Paris with a piece of the meteorite where he’s able to harness the power of Radium X for good, helping to cure the blind. But he’s also planning to take his revenge on Drake and begins to murder the members of the African expedition.

Despite opening with all those Gothic trappings and ending with a mad killer on the loose, The Invisible Ray is really more science fiction than it is horror, though its grasp of even the basic tenets of science, particularly astronomy, is extremely shaky – Andromeda, a galaxy, is repeatedly referred to as a nebula, for example, and it’s 2.5 million light years from Earth, not the mere “three quarters of a million” Rukh claims. His telescope is more a thing of fantasy than proper science fiction and the talk of Radium was inspired, no doubt, by the early 20th century fad for the element, when it was being peddled by quack “doctors” as a cure-all for just about everything. Only in the 30s did the more detrimental effects of radium become widely known and it’s possible that The Invisible Ray was buying into this increased interest.

But while writer John Colton might have not really understood science, he knew how to put together a fun, action-packed script that Hillyer, replacing Stuart Walker who left the film early in production, does a smart enough job translating to the screen. Lambert Hillyer had a busy 1936 with Dracula’s Daughter also in release and he enjoyed a hugely prolific career, directing the first screen appearance of one of the most popular of all comic book heroes in the 1943 serial Batman, and more B-westerns than you can shake a stick at, including the popular Cisco Kid series. His handling of The Invisible Ray is assured if not particularly distinctive, and the film’s best moments are those created by Universal’s veteran effects man, John P. Fulton, who’s given free rein to try out his whole bag of tricks here – and very good they are too.

It’s all utterly absurd (and, in its presentation of Africans as gibbering, fearful imbeciles, as racist as you’d expect from a Hollywood film in the 1930s) but thanks to good performances from Karloff and Lugosi, some great sets and special effects that would later be recycled for the serial Flash Gordon (), it all just about works. For Karloff, this was an early outlier of the kind of “mad scientist” roles he was going to getting a lot of in the coming years. In particular, he appeared as a string of misguided researchers in films for Columbia and Monogram.

To make the film work, you do have a to jump through a lot of loops, accepting that the science is as loopy as it gets (it’s really best not to think about any of it), trying not to worry that Cooper, sporting unconvincing old age makeup, was only actually a year older than her screen son, and just enjoying the silliness of it all. There are some great moments here – Rukh melting an African rock with his newly built death ray, some lovely matte paintings that distract you away from how ridiculous Rukh’s demonstration of his telescope is and the scientist’s ultimate fate, leaping from a window and bursting into flames as the Radium X finally consumes him. If the third act drags a bit, there’s much pleasure to be had from the studio-and-backlot Africa and while The Invisible Ray is very far from the best of Universal’s genre films of the 1930s, it’s a lot of simple fun.