The Alden children are visiting Aunt Jane for the summer in Elmwood. When they go to visit the general store, they realize that the owner needs some help, so the kids volunteer to work. But the Aldens soon discover that there is something strange about the shopgirl, Nancy. She has worked at many different jobs but has a hard time remembering how to work the cash register and becomes nervous and flustered when the store gets busy. Plus things at the store start to go missing. Can the Boxcar Children figure out this mystery about Nancy? #28 in the series.
The Boxcar Children are working in a general store to help out a friend of Aunt Jane's. The nervous, secretive girl who also works there intrigues them, and when a strange man comes to the store asking about her, the children feel it's time to investigate.