This is a condensed version of the full serial, The Phantom Creeps, and boy I'm happy Rifftrax didn't do the full 4 plus hour run! I recall fondly watching Mystery Science Theater 3000 version's riff the first 3 episodes of this serial and fans have edited them together on Youtube, but if you were curious about how it ended, I recommend checking this version out also with riffing. There is also a condensed non-riffed film version that runs about 90 minutes where they cut out the cliff hangers (I guess), I saw that was also posted on Youtube. If I was a young boy in the theaters watching this in 1939 I would have been very entertained, as an adult in the year 2023 this serial lacks a lot of excitement and is very repetitive, its not in the top tier of film serials in any way and I say that as a big Lugosi fan. This Rifftrax version runs just over 60 minutes and that's enough of this silliness for me. The opening of the serial has plenty of cool weapons and gadgets like invisibility and suspended animation gas, and then there is the robot! This robot is remote controlled so its not on the smart side. It's tint is a very dark black color and it's face reminds me of an African caricature which I'm sure was intentional and in 2023 could be considered racist, but unfortunately you get a lot of those things in 1930s films. Rifftrax has posted a preview for free on Youtube and its also available as a pay per view purchase on their website. I watched it with limited commercial breaks on Tubi for free and I also saw that its available free on Pluto TV. Tubi I think has less commercial breaks then Pluto so I recommend watching it there. Although I never watched it as originally released, my guess is I would rate the straight serial a 4, the MST3K and Rifftrax versions an 8. As Bela would say, Now I shall have my revenge with my army of robots! (hint, he only had one robot, lol).
