Anna Katharine Green 
A Strange Disappearance 

This book is the second in a series that stars Gryce and his associate Q. They are asked to look into the potential abduction of the family seamstress by Mrs. Daniels, a domestic worker at a Mr. Blake's home. The narrative moves slowly at first, but picks up speed as the plot develops and we learn more about the who, what, how, when, where, and why of the case. Although there is major romance in the book, the ladies are not naive simpletons. They are strong people who can make sacrifices for the people they care about.