Released 20 January 1936, The Invisible Ray was the third of the eight films Boris Karloff and Béla Lugosi made together. Initially, their next teaming had been planned as Bluebeard, but the script wasn’t ready in time. The powers that be put Bluebeard on the back burner and instead found a different film.
Director Stuart Walker didn’t like John Colton’s script for The Invisible Ray, and asked for a three-day break to fix it. When Universal refused, Mr. Walker left, and was replaced by Lambert Hillyer.
The initial budget was $166,875, considered fairly lavish for a B-movie. The production went over by $68,000, as well as going over schedule (17 September–25 October 1935). According to Stuart, “The director who did the picture started nine or ten days after I was ordered to start and finished 25 or more days after I was ordered to finish.”
Dr. Janos Rukh, like many mad scientists in the tradition before him, is widely seen as a crank whose obsessive research and unusual theories are an embarrassment and ridiculous vanity project. However, he’s bound and determined to prove his work is on the level and that he’s on the verge of the next great scientific breakthrough.
Towards that end, he convinces two such naysayers, Dr. Felix Benet (Lugosi) and Sir Dr. Francis Stevens (Walter Kingsford), to come to his home for a demonstration of a fascinating new telescope. Francis also brings his wife, Lady Arabella Stevens (Beulah Bondi), and his nephew Ronald Drake (Frank Lawton).
Predictably, Dr. Rukh’s much-younger and very pretty wife of three years, Diana (Frances Drake), has an immediate and mutual attraction to Ronald. Diana’s father was Dr. Rukh’s assistant, and when he passed away, she dutifully married Dr. Rukh. However, she’s never felt romantic love for him.
When everyone is seated, Dr. Rukh gives a marvellous demonstration of a new telescope, along with narration. The telescope not only gives a great planetarium show, it also projects images from millions of years ago. One of these images is a meteorite striking somewhere in Africa.
Drs. Benet and Stevens are so impressed by this magical telescope, they abandon their former hardened skepticism and agree to accompany Dr. Rukh on an expedition to find the impact site and harvest the material in this ancient meteorite.
The African quest takes far longer than expected, and nothing has been found. Though the others are starting to have second thoughts and planning to return to England soon, Dr. Rukh insists on staying just a bit longer. He feels he’s on the verge of a breakthrough in discovering the impact site, and with it incredible scientific secrets.
Find it he does, with the help of a bunch of natives. As per the unfortunate standards of most films of this era, they’re depicted as easily-spooked and having really cartoonish reactions to their fear.
Though Dr. Rukh is delighted to discover not only the impact site but the actual meteorite itself, his excitement is short-lived. When the meteorite is exposed to daylight again, it explodes and sends out dangerous radiation which sickens him quite badly. Dr. Rukh now glows in the dark, and his touch is deadly.
Dr. Benet compassionately creates an antidote which Dr. Rukh must take at the same time every day. If he doesn’t inject himself religiously, he’ll go back to his fully radioactive state. However, the newly-discovered element Radium X may have permanently altered his brain, and eventual madness may descend. The antidote also isn’t a cure, just a means of keeping the worst effects under control.
After Dr. Rukh returns to base camp, Dr. Benet tells him of the secret romance between Diana and Ronald. Knowing full well Diana never loved him, Dr. Rukh fakes his own death shortly after coming to Paris. He finds a man who very much resembles him, murders him, and makes him look like he died of radiation poisoning.
Dr. Benet returns to Europe with a piece of the meteorite and uses its powers for good. His procedure for curing blindness is embraced as a miracle. He also cures other ailments with a modified form of Radium X.
Though Dr. Rukh also uses Radium X to cure his mother’s blindness, his altruism doesn’t last for long. He presently sets his mind firmly upon revenge, and takes up residence in a boardinghouse across the street from a church with six statues. Each figure represents to him one member of the African expedition, and thus the people he believes ruined his life by getting rich and famous off of his discovery and hard work.
And thus begins a reign of terror from a mysterious invisible force.