Carolyn Keene

By mistake Nancy Drew receives a letter from England intended for an heiress, also named Nancy Drew. When Nancy undertakes a search for the missing young woman, it becomes obvious that a ruthless, dangerous man is determined to prevent her from finding the heiress or himself. Clues that Nancy unearths lead her to …

The Clue in the Crumbling Wall is the twenty-second volume in the Nancy Drew Mystery Stories series. It was first published in 1945 under Carolyn Keene, a pseudonym of the ghostwriter Mildred Wirt Benson.

The Invisible Intruder is the 46th volume in the Nancy Drew Mystery Stories series. It was first published in 1969 under Carolyn Keene. The actual author was ghostwriter Harriet Stratemeyer Adams.