The hidden staircase

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. The original text was written by Mildred Wirt Benson, who said that it was her personal favorite of the Nancy Drew Books she wrote. The novel was adapted as a Warner Bros. film, Nancy Drew and the Hidden Staircase, in 1939. Another adaptation of the book from Warner Bros. was released on March 15, 2019. (This summary is from Wikipedia.)

Summary written by Project Gutenberg, by machine.