The Mystery of the Lost Mine — Gertrude Chandler Warner

One warm night four children stood in front of a bakery. No one knew them. No one knew where they had come from.

Henry, Jessie, Violet, and Benny used to live alone in a boxcar. Now they have a home with their grandfather, and they're going on a trip to the Arizona desert.

There the Aldens learn about the legend of the Lost Dutchman Mine. Everyone thinks the mine is filled with gold. Can the Aldens find out if the legend is true, and if it is, who will find the gold?