Vincent Price is Gallico the Great, a magician who has a new act he invented that involves cutting a woman in half with a huge buzz saw. But the company he works for insists that everything he invents belongs to them--and they want this new act to go to another magician, Rinaldi the Great, who is his nemesis. The magician ends up beheading his boss--and he almost gets caught when an assistant accidently takes the duffel bag he put the guy's head in. The magician, via makeup, impersonates his former employer and has to kill his wife (Eva Gabor) when she realizes it isn't her husband. He becomes crazier and crazier. In the end he meets his fate with a new diabolical invention, The Crematorium, when he tries to kill the detective who is on to him.
This features Price at his best and I can see how this led to him being cast in similar roles (the Roger Corman films, DR. PHIBES, et cetera). Weirdly, this has the feel of a William Castle film. Recommended.