It's October and you should be watching horror movies during every waking hour. But, since you are here, let's talk about The Invisible Ray. You can really tell that the makers of the movie were banking heavily on Karloff/Lugosi interactions selling this thing. It's evident in the slow-tease reveal of Karloff's character and in the way the horror legends' face-to-face interactions are framed.
But you can't make a movie based only on two stars being filmed together (as From Justin to Kelly taught mankind). So we get a story that's steeped in wackaloon science, with Earth's past reflected in cosmic rays and Karloff's scientist character searching out "Radium X" deposits in Africa. The Africa scenes are probably going to be tough for modern viewers to stomach. Not only do we have Tarzan speak ("Me want go too!"), but the non-Karloff/non-Lugosi characters are serious jerkoffs to the poor natives. The Invisible Man asks us to care about the romance of one character when she's bitchily berating her dusky assistants in previous scenes. Some of the non-K/non-L cast are good actors, but the subplots aren't all that compelling, especially the romance stuff, which seems very undercooked.
So, anyway, Karloff's character gets Radium X poisoning. This causes him to glow in a special effect that looks awfully crude to 2014 eyes. The upside is that it allows him to kill just by touch. The downside is that it is slowly killing him. Fortunately, Lugosi's rival scientist has an antidote. And, fortunately, he tells Karloff, in a scene of more splendid science bullshit, that he has to take the antidote periodically or "you will literally crumble to ash!"
Radium X and the anti-Radium X serum turn brains bad, I guess, and Karloff starts killing and this becomes a horror film after all. It's not an exceptionally good or compelling one, and I'd argue that it would mostly be forgotten if it didn't have its two stars in the cast. The acting works throughout the film, but there's not enough meat to the story to keep you engaged. Add in the shoddy effects and the casual racism and it's tough to love The Invisible Ray. A pretty mediocre start to this year's 31 Days of Horror!!!~!