The Halperin brothers had just independently made the really bad but curiously watchable WHITE ZOMBIE. Paramount subsequently hired these cash magnets to make this low budget for the studio )but massive budget for the Halperins) hour of nonsense. It's quite fun.
It's utterly ridiculous which is what makes it so fun. H B Warner's solemn and theatrical delivery of his lines explaining in all seriousness how he's invented a machine to use 'microgenic' rays to extract 'the soul' from the dead adds to the silliness. It's especially crazy as he says all this to the jail warden who simply accepts all this gibberish as absolute common sense..... and lends the doctor the body of the executed criminal to experiment on - as you do!
That old style acting in this picture (although this is ten times more natural than in WHITE ZOMBIE) is perfect for an over-the-top, moody 'horror' film like this. Naturalist and believable acting in a big kids' fairytale world have been weird. When it came out audiences were thrilled and scared - today you'll be entertained by its daftness.
It's one of those pictures made by innovative, imaginative 'amateurs' which don't look as professional as films made by 'proper' directors but the enthusiasm of the Halperin brothers (and Paramount's budget) makes this worth watching.