Andy Siems’s review published on Letterboxd :
You take some sci-fi mad scientist stuff, mix it up with Dr. Jekyll & Mr. Hyde horror and then wrap it all in a gangster picture and you have the utter silliness that is Black Friday. Why is it even called Black Friday? In this low grade, on the cheap B-Movie, Boris Karloff stars as Dr. Ernest Sovac who, while trying to save his best friend's life AND further his illegal and un-ethical brain transplant theories switches brain sections from a Gangster crime Lord with a mild mannered English Literature Professor. Before long this becomes a Jekyll & Hyde picture in Gangland. Leading the local mob in a sad and almost non-existent role is former screen giant Bela Lugosi who walks through his wasted screen time. Sadly this was Karloff and Lugosi's last team-up for Universal and yet they never appear on-screen together for a single moment. What a waste (especially when you consider how amazing they were together in The Black Cat). The stand out performance in this movie is that of Stanley Ridges, Prof. George Kingsley / Red Cannon in a near duel role. The swings in character from the sweet Professor to the Hyde-like Gangster is so complete that I had to look at the credits to see if it was played by two different people. Sadly, those personality/brain switches really just comes off as DUMB. His hair changes color, his vocal range pitch changes and, of course he becomes so aggressive that he is responsible for multiple murders. Like I said this obvious Jekyll & Hyde re-imagining mixed with a gangster splash might have sounded interesting in the studio board room, but on screen it feels laughable.