Disappointing movie if only because Karloff and Lugosi do not share a single scene together and they pretty much play second and third fiddle to Stanley Ridges who was okay in a dual role. Otherwise a bland movie.

Stanley Ridges ("Prof. Kingsley") is seriously ill when Boris Karloff ("Dr. Sovac") performs a highly unethical operation to replace his brain with that of gangster "Red Cannon". Though successful in prolonging his friend's life, the newly invigorated Professor begins to demonstrate quite a few of the less savoury character flaws/traits of "Cannon". "Sovac" learns from one of these episodes that there is $500,000 hidden away somewhere, so he attempts to manipulate his friend to reveal the location of the loot. It's billed as a Karloff and Lugosi feature - but some recasting shenanigans meant that they never ended up appearing in a scene together, but that doesn't really matter - this is more of a sci-fi thriller than a horror film, and neither of their performance are really much to write home about, anyway. The star is Ridges who juggles his split personalities quite well whilst Arthur Lubin keeps the story moving along well enough. Sadly, though, it's all just a bit unremarkable with a fairly standard structure and ending.