Lady and the Monster was the first film version of the classic Curt Siodmak sci-fi/horror tale Donovan's Brain. The plot involves the brain of a famous but unscrupulous financier, recently deceased. The brain is kept alive artificially by overenthusiastic scientist Erich Von Stroheim, with the help of lab assistants Vera Hruba Ralston (the "lady" of the title) and Richard Arlen. Gradually, the dead financier's brain takes over the mind of Arlen, turning him into the helpless conduit for the financier's evil machinations. Lady and the Monster was remade in 1954, using the original Siodmak title Donovan's Brain.
by Hal Erickson synopsis