The secret of the old clock

The Secret of the Old Clock is the first volume in the Nancy Drew Mystery Stories series, written under the pseudonym Carolyn Keene. It was first published on April 28, 1930, and rewritten in 1959 by Harriet Stratemeyer Adams. On January 1, 2026, the original version of the novel entered the public domain in the USA.
Nancy Drew is a sixteen-year-old high school graduate (her age was changed to eighteen in the 1959 rewrite). Her father, Carson Drew, is a well-known criminal defense lawyer. The Drews reside in River Heights and employ a housekeeper, Hannah Gruen. In early editions, she is depicted as a mere servant; later in the series, she becomes more of a family member.
In 2001, the novel ranked 53rd on Publishers Weekly's list of the all-time best-selling hardcover children's books in English, having sold about 2.7 million copies. (This summary is from Wikipedia.)