She Devil (1957)

Hot on the heels of his successful sci-fier Kronos, Kurt Neumann directed the lesser genre entry She Devil. Jack Kelly stars as a doctor who invents a miracle cure for several horrible diseases. Suffering from tuberculosis, Mari Blanchard agrees to test out Kelly's wonder serum. Almost instantly, Mari's health and strength are restored. Unfortunately, there is one teeny-tiny side effect: Mari's benign personality transforms into that of a scheming predator with a pronounced homicidal streak. As Kelly and his superior Albert Dekker stand by helplessly, Mari murders the wife (Fay Baker) of wealthy John Archer, then draws up plans to knock him off and claim his millions. Even back in 1957, no one took this one seriously.