This is an entry from my Essential Horror book. Mad Love was Peter Lorre's first American movie after years climbing the European ladder of stardom (most notably with the excellent "M"). This one is actually a retelling of The Hands of Orlac from the point of view of the mad scientist who gets the whole ball rolling. Whereas the original followed Orlac slowly going insane, this one shows all the machinations of Dr. Gogol as he tries to steal Orlac's wife away (a motivation I don't recall from the original).
It starts with Orlac's wife performing at the Grand Guignol in Paris. If this was a real thing, and I'm pretty sure it was, I would have loved it. It was like Medieval Times for Horror fans. People would buy tickets to see torture re-enactments. There were waxworks and the the employees all dressed like demons. Dr. Gogol has been buying an expensive box seat every night to watch Orlac's wife perform. He even buys her wax statue when he learns they are throwing it out.
I must say, the plot makes less sense this way. Orlac's father has a much diminished role and the bit about the killer having his head re-attached just doesn't play because you immediately know it is Lorre under the disguise. Still, his sweaty, greasy performance is pretty wonderful and makes you feel super creeped out no matter how sympathetic the script tries to make him.
All in all, Mad Love is just ok.