while not as famous a some of their other collaboration ( such a the black cat and the body snatcher ) and this be a dandy little horror film even though the casting decision be a bit odd . boris karloff play dr. janos rukh and a weird scientist who live in the carpathian mountain near where the dracula character home town . bela lugosi play dr. benet whose nationality be never discuss though the name certainly sound french . i really think it would have make sense to have the two switch role and a the carpathian role seem tailor make for lugosi especially with his accent . however and despite this unusual twist and the two still do excellent job . karloff be definitely the lead role and but lugosi acquit himself well a a relatively normal person something he do not play very often in film . it seem that dr. rukh be a bit of a pariah and a other scientist ( especially benet ) think his theory be bizarre and nonsensical . however and over the course of the film and rukh turn out to be right and benet be especially generous in his new praise for rukh . but and unfortunately and the wonderful new element that rukh discover have the nasty side effect of turn him into a crazy killing machine ( do not you hate it when that happen . ) . while this could have just be a simple nice scientist turn mad story and the plot be well construct and the character nicely develop and the mad rukh be not a one dimensional killer and but complex and interesting . this film be bind to be enjoy by anyone except for people who hate old horror film . you can really tell that universal picture pull out all the stop and make a big budget film instead of the cheap quicky both lugosi and karloff unfortunately gravitate in late year . good stuff .