Locked Doors by Mary Roberts Rinehart

Mary Roberts Rinehart was a prolific writer that is often referred to as the American Agatha Christie.  Rinehart's mystery novels are still treasured by millions of readers today and she is the source of the famous phrase "The butler did it."  Rinehart's most famous books include The Circular Staircase, The Bat, The Case of Jennie Brice, and The Door.

Locked Doors, published in 1914, is a thriller full of mystery and suspense that follows Miss Adams, a nurse turned detective, who investigates a large house where all the doors are locked at night.