Black Friday

Karloff stars as a surgeon who's close friend Stanley Ridges is fatally wounded in a car accident with a notorious gangster. To save his life, Karloff transplants part of the gangster's brain into his friend's head, killing the gangster in the process. Karloff realizes that the gangster's personality is preserved in his friend's brain, and decides to exploit this to find out where a missing stash of $500,000 is hidden. An interesting take on Jekyll and Hyde with Ridges changing back and forth between a mild mannered English professor and a ruthless gangster, with Karloff playing the scientist who increasingly loses perspective on how badly he's exploiting his friend. Lugosi is here too in the extremely questionable role as a rival gangster. He's okay ... but he's very obviously wrong for this part.