Henry, Jessie, Violet, and Benny used to live alone in a boxcar. Now they have a home with their grandfather, and they are working at a mall owned by his friend. When the Aldens arrive at Hope Harbor, they're excited to see the crowds of shoppers and the endless variety of stores. But as they begin to work at Penny's Emporium, a novelty shop in the mall, everything starts to go wrong. Some of the other mall workers don't seem to want the Aldens' help. Even worse, some of the merchandise bound for Penny's Emporium has disappeared. What's going on at Hope Harbor Mall? It's up to the Boxcar Children to figure out who's behind this mystery.