Mystery Girl

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.