Infamous burglar "The Bat" commits a daring jewelry theft despite heavy police presence. Soon after, a bank theft occurs, which may be the work of the criminal as well. Meanwhile, Cornelia Van Gorder has various people arrive at her old mansion, including her niece, Dale, a bank employee, and police detective Anderson. When guests start turning up dead, Cornelia begins to suspect that The Bat may be lurking around the estate.
A masked criminal who dresses like a giant bat terrorizes the guests at an old house rented by a mystery writer.
Chick Williams, a prohibition gangster, rejoins his mob soon after being released from prison. When a policeman is murdered during a robbery, he falls under suspicion. The gangster took Joan, a policeman's daughter, to the theater, sneaked out during the intermission to commit the crime, then used her to support his alibi. The detective squad employs its most sophisticated and barbaric techniques, including planting an undercover agent in the gang, to bring him to justice.
