The Hidden Staircase is the second volume in the Nancy Drew Mystery Stories series written under the pseudonym Carolyn Keene, published in 1930 and revised in 1959.

[1] The original text was written by Mildred Wirt Benson, and she has said that it is her personal favorite of the Nancy Drew Books she wrote.

At the beginning of the original edition of The Hidden Staircase Nancy is home alone while her father and their housekeeper, Hannah Gruen, are both out for the day.

The doorbell rings and Nancy is introduced to the "rude visitor," Nathan Gombet, who has come to see Carson Drew about some papers.

When his persistence irritates and insults Nancy, she grows impatient and angrily tells him to leave and threatens to call the police.

The sisters explain that numerous valuable items have gone missing from their Civil War-era mansion, but they cannot understand how any person could have entered the locked home during these different instances to commit the thefts.

They decide that when he knows the day of his arrival back in River Heights, Nancy will pick him up at the train station to discuss her findings at the Turnbull mansion.

After an enjoyable dance with her former prom date, Nancy and her father inspect the railroad construction near the river but are forced to swim to safety when a runaway truck nearly runs them down.

A chandelier moving by itself, and a mask held up in the windows over the next few days lead Nancy to investigate the interior and exterior of the Colonial house thoroughly.

In the meantime, Nancy's father fails to return from Chicago, and after tracing him to the train station, she is led to believe from eyewitness accounts that he has possibly been drugged and kidnapped.

Nancy continues to search for clues to her father's whereabouts and also to solve the mystery of the intruder at Twin Elms, helped by a night watchman and discovery of a secret room.

She and Helen decide to investigate the neighboring estate for clues to a secret entrance since the house was built with the same design as Twin Elms.

Nancy discovers a missing property owner, hidden staircases and passages inside Twin Elms; with police help, she finds her father imprisoned in a room off the tunnel.