Stanley Ridges, playing "Prof. Kingsley," suffers from a grave illness, which leads Boris Karloff ("Dr. Sovac") to carry out an improper procedure involving brain transplantation—specifically, replacing his friend’s brain with that of the gangster “Red Cannon.” The operation succeeds in keeping Ridges alive, but the Professor starts exhibiting several undesirable qualities associated with "Cannon." "Sovac" discovers …

It's disappointing to see that Karloff and Lugosi never appear together on screen, as they are relegated to supporting roles behind Stanley Ridges’ performance in a double part, which wasn’t particularly memorable. Aside from that, the film itself is rather unremarkable.