The story follows the efforts of the authorities and Cornelia Van Gorder, a popular mystery novelist, to apprehend a mysterious costumed killer known only as "The Bat." The masked fiend leaves a trail of mutilated corpses in his wake as he prowls the night in search of stolen loot rumored to be hidden somewhere in the country home occupied by Van Gorder and her entourage.
Price turns in a typically charismatic, quietly sinister performance as a doctor drawn into the hunt for the buried treasure, but it is Moorehead's Mrs. Van Gorder, or "Miss Corny" as she is affectionately known by her loyal but petrified maid Lizzy (played by Lenita Lane), who steals the show.
As the bodies pile up, the cops get involved but they are revealed to be bumbling and useless at practically every turn. Only Van Gorder, a fearless, unflappable, self-fashioned sleuth, proves to be a match for the ruthless Bat in this chilling game of death with a cool million in unclaimed bank securities up for grabs.