The White City Disappearance by Cate Martin

Dorothy Lundegaard helps her brother John run Lundegaard Investigations, a business their father ran from his retirement from the St. Paul, Minnesota, police force until his death in 1935. The business just barely ekes by, but helping people with problems means more to Dottie than any other work she could possibly find.

People like Charles Meyer, a man still holding out hope for the sister he hasn't seen since the day her hand slipped out of his while walking through the World's Columbian Exposition in Chicago in 1893. Just sixteen, and never seen again.

Her disappearance is the coldest of their father's cold cases, the one he never solved despite decades of effort. But Dottie possesses resources her father never had. Maybe, just maybe, she can help her brother finish the work their father started so many years ago.

"The White City Disappearance," a short story in the continuing Dorothy Lundegaard Mysteries.