Doctor Dan Scott (Jack Kelly) invents a serum that cures illness and Kyra Zlus (Mari Blanchard), dying of tuberculosis, agrees to be a guinea pig. She becomes well and strong, but develops strange characteristics and a scheming personality. She kills Evelyn Kendall (Fay Baker) in order to marry her wealthy husband, Barton Kendall (John Archer) and later kills him to inherit his wealth. Dr. Scott and his associate, Dr. Richard Bach (Albert Dekker) decide that something drastic must be done and they trick her into having an operation.