Captain Midnight does battle with a supervillain named Ivan Shark over a new invention known as the Range-Finder.
Who is Captain Midnight? He's the secret hero identity of Captain Albright, and is recognized by his black mask and goggles which obscure his face (and most likely his peripheral vision). Wait! Scratch that word "secret"; as far as I can tell, everyone knows who he is fairly early on in the proceedings here, so I'd hardly call it "secret." His name strikes fear into the hearts of outlaws! Why? Uh...I'm not sure; his main talent appears to be a willingness to get into fist fights with three or four criminals at the same time—and getting soundly pummelled. On the other hand, he has dogged persistence, and seems to inspire massive waves of stupidity in his foes; they miss every easy opportunity to kill this guy. That's because Ivan Shark keeps wanting to use his elaborate death rooms to kill him, including one of those trick rooms with steel walls that fills up with water, a rotating fire trap room, and (as God is my witness) a room with a big log and circular saw to cut it in half; I was actually disappointed he never got around to tying him to a railroad track.
Okay, I'm probably making this serial more fun than I found it to be; actually, I thought it was one of the duller ones I've seen lately. However, I'm probably in the minority here; it probably appeals to those who like their serials crammed with action but unhampered by troublesome details like an interesting story. Incidentally, the Range-Finder (I'm not entirely sure what it does; maybe it's used to locate your enemy's stoves) is the only science fiction element of the script.