This is book number 28 in the The Boxcar Children Mysteries series.
Henry, Jessie, Violet, and Benny are working in a general store, to help out a friend of Aunt Jane’s. It seems to the children that the young girl who works in the store is behaving very strangely. She seems nervous and won’t answer any questions about her past. Then a strange man comes to the store asking about her. What secret is the mystery girl hiding?
The Boxcar Children Series was created by Gertrude Chandler Warner, a teacher, when she realized that there were few, if any, books for children that were both easy and fun to read. She drew on her own experiences in writing the mysteries. As a child, she had spent hours watching trains near her home, and often dreamed about what it would be like to live in a caboose or freight car. In each story, she chose a special setting and introduced unpredictable, unusual or eccentric characters, to help highlight the Aldens’ independence and resourcefulness. Miss Warner lived in Putnam, Massachusetts until her death in 1979.