This one is a pretty solid story. Not really so much science fiction - that is to say, there is a science device shoehorned into it, but at its core, it's really a creepy little revenge tale, with cops trying to figure out whodunit.
The main character arrives home from a trip, only to be met by his best friend's anxious man-servant. The Professor has disappeared, you see. Going to his house yields a creepy laboratory, with a glass cage with no obvious entrance, and the Professor's diamond ring upon the floor of the cage. Has he disappeared? Is he dead? And who was that mysterious man who showed up at the door the night before?
The main character is immediately suspected by the police, as the Professor's heir, and they are determined to pin this murder on him. But in the end, it turns out that another crime entirely has been committed, with the help of "absolute zero." In this case, you could pretty much substitute "disintegrating death ray" for "absolute zero" and it would mean the same thing. I'm not sure the author really knows what absolute zero is.
But yet again, here's a scientist who ends up committing an atrocious act - less from scientific hubris this time than from personal motives for revenge, but the mad scientist using his science for evil has been a theme in, what, three of the five stories I've read so far? And of the other two, one had a scientist who was perfectly happy to suppress evidence that could save lives in order to keep his own career secure.
For science fiction, those who commit science are not coming off well in 1930. At least not in this magazine. There is a definite feel both that there are unimagined natural horrors around every corner that could leap out and bite us, as well as that what those scientists are up to in their labs can't possibly be good.
Gender? The only woman is the man-servant's wife, and she barely appears. The scientist deeds the house to the couple, so that's nice. And there's a woman in the backstory, a woman who betrayed the scientist and set him on his mad path to homicide. As, you know, women do?
Race? No mention.
The cops? Slightly dumb, but trustworthy, and out to get their man.
Sexuality? You've got to be kidding me. I'm not expecting anything overt - although I swear that one story was so full of innuendo it was overflowing. I'm not expecting to find anything but heterosexuality here, but it's worth pointing out that that's the case. Stepping away more broadly, that dame in the backstory is suggested to have been actively sexual - and of course, that's part of the problem with her. Sex makes women evil, people.
Two more stories after this, and I'm done this issue!