The Hidden Staircase is the second book in the original Nancy Drew Mystery Stories.
In the original 1930 version of the story, Nancy is introduced to the Turnbull sisters by Abby Rowen, a character aided in the resolution of the first volume. The complaint is that their home, "The Mansion," is haunted. Nancy's father is being harassed by a crooked character, Nathan Gomber. Gombet threatens violence. Carson Drew, undaunted, agrees to allow Nancy to investigate the Mansion, and sends his revolver with her. He will travel to Chicago during the first part of Nancy's stay at the old estate, and join her later.Nancy discovers odd happenings at the Mansion, which is primitive--it lacks electricity. A valuable pin has been stolen, and canaries get into the house of their own accord. Nancy can't focus on the mystery, when her father fails to arrive home from Chicago. He appears to have vanished. Meanwhile, Nancy finds out that the nefarious Gombet owns the adjacent estate, very similar in appearance to "The Mansion." She decides to investigate one rainy night, armed with revolver and electric torch. She successfully breaks into the basement, but must hide and evade Gombet's accomplice and housekeeper, a large, ill-tempered African American woman. While roaming around the odd house, Nancy accidentally falls through a secret panel and down a staircase, discovering a tunnel. Her exploration leads her back to the attic of the home where she is staying, up another series of staircases.
Nancy reveals her discovery to the elderly Turnbulls in the morning, then they investigate together. Police, based on Nancy's suspicions, raid Gombet's house, where Carson Drew has been a prisoner for days. Gombet was behind the hauntings as well.
In the 1959 version, Helen and her great aunt Rosemary ask Nancy to solve a mystery at her great-grandmother's home, Twin Elms, a stately Colonial mansion in nearby Cliffwood. Odd things, beyond the eccentricities of the elderly Miss Flora, are happening. In the meantime, Nancy's father is being threatened by crooked lawyer Nathan Gomber, who feels Carson, as attorney for the railroad, cheated property owners near a new railroad bridge. His client, Willie Wharton, is holding up proceedings by hiding. Nancy and her father view the railroad bridge after church, and must swim to safety to escape a runaway truck at the site.
Nancy and Helen go to stay at Twin Elms while Carson goes to Chicago to find Wharton. The girls first day, a chandelier sways by itself. Miss Flora is missing items, music comes out of nowhere, and a gorilla is seen peering in a window. Nancy and Helen explore more about the history of the house and grounds. After Nancy confers with the local chief of police, an officer named Patrick is assigned to patrol the grounds -- his first capture, Nancy! Nathan Gomber harasses Miss Flora and Rosemary to sell their property repeatedly.
Carson fails to arrive, worrying Nancy. All four women did period costumes for an evening of fun. Meanwhile, she tracks down a newspaper discovered near the Twin Elms estate. Unfortunately, this lead is delayed when the ceiling of the front hall falls in on Nancy and Helen. Nancy and Helen even explore the roof---where Nancy notices the "twin" estate, Riverside Manor, which is for sale. The girls also discover a hidden "listening post," in a secret room adjacent to the kitchen.
A Realtor gives Nancy the key to Riverside Manor, even though it has been sold. Nathan Gomber owns Riverview Manor. She and Helen explore the twin property, and Nancy discovers a hidden panel, falling down a hidden staircase. She and Helen explore a tunnel leading back to another staircase---and run into none other than Willie Wharton! The girls reveal the tunnel and the staircases to Miss Flora and Aunt Rosemary. Gomber is apprehended, and leads police to a hidden room in the tunnel, where Carson Drew is kept prisoner.
The original Russell H. Tandy artwork features Nancy in a 1930 raincoat and hat, climbing the hidden staircase by flashlight. An updated version, in 1950, shows Nancy opening the panel to the staircase for the Turnbulls. This scene was retained for the revised text in 1959, and was actually described in the book in detail. In 1966, the art was replaced with Rudy Nappi's matronly Nancy, in an updated version of the original Tandy art. The revised text story was published as a book club edition in 1960. Polly Bolian illustrates Nancy and Helen on the cover, by flashlight, investigating the tunnel with the stairs behind them.
The Hidden Staircase was filmed in 1939 by Warner Brothers as Nancy Drew and the Hidden Staircase, part of their series of four films starring Bonita Granville as Nancy Drew. The plot was heavily revised for the film. Nancy's father is not harassed by anyone, and the plot becomes a murder mystery when the Turnbull sisters' chauffeur is murdered and the death is made to look like a suicide.