A mad doctor, Van Sloan, is the head of a drug syndicate. When he knocks off people who know too much, he doesn't fill the caskets with their bodies, but with dope. Karloff, in his first role following FRANKENSTEIN, is merely another thug helping Secret Service agent Holt, a disappointment
for his legion of fans. Despite the serial-like plot of storm-raging nights, eerie graveyards, and a laboratory crackling with strange electrical instruments, the film packs a lot of campy interest. Van Sloan, the kindly, moralistic character of DRACULA and FRANKENSTEIN, here turns lunatic,
savoring the vivisection of his victims.