A mysterious criminal by the name of "The Bat" eludes police and then finally announces his retirement to the country.
In the countryside near the town of Oakdale, news of a bank robbery in Oakdale has put Mrs. Van Gordnerâs maid, Lizzie, on edge. Mrs. Van Gordner is leasing the house from Mr. Fleming, the Oakdale bank president, who is in Europe. The chief suspect in the bank robbery, a cashier, has disappeared. Mrs. Van Gordnerâs niece, Dale arrives followed by the gardener she has hired. Dr. Venrees arrives and tell Mrs. Van Gordner that he has received a telegram from Fleming stating that because of the robbery he will be returning soon and will need to occupy his house.
There are mysterious noises in the house and lights turning on and off. A rock is thrown the window with a note threatening harm if the occupants donât leave. Dale, and the gardener, who is actually Brook, the missing teller, are looking for a secret room in the house. They believe the money from the robbery is hidden there.
Detective Anderson shows up and questions Mrs. Van Gordner. Mr. Flemingâs nephew, Richard, arrives at Daleâs request. She is hoping he can help in finding the secret room. Richard finds the house plans but refuses to show them to Dale. He pushes her away and runs up the stairs but he is shot by someone at the top of the stairs and falls dead. Mrs. Van Gordner sends for a private detective.
A mysterious masked man sticks a gun in the caretakerâs back and tell him he better get everyone out of the house. The lights continue to go on and off. The shadow of the Bat is seen by various occupants of the house.
Anderson states that Fleming isnât in Europe but robbed his own bank. He accuses the doctor of being part of the plot.
An unconscious man is found in the garage. He comes to and is questioned by Anderson. He canât remember anything. Anderson tells the private detective to keep an eye on him.
The hidden room and the missing money are found. Fleming, the missing banker, is found dead behind a wall in the room. The garage suddenly bursts into flames. In the ensuring chaos, the Bat appears and is caught, but he gets away before he can be unmasked.
As the Bat is fleeing from the house, he is caught in a bear trap, set up by Lizzie. He is revealed to be Anderson, who isnât actually Anderson. The real Detective Anderson is the man who was found unconscious. The bat says no jail can hold him and he will escape.
A curtain closes across the screen. We are in a theater. Chester Morris, who played Detective Anderson tells the audience that as long as they donât reveal the Batâs identity they will be safe from the Bat.
Where do Brook  and Dale think the money from the robbery is hidden?
secret room in the house