In The Double Cousins and the Mystery of Custer's Gold by Miriam Jones Bradley, the Double Cousins find an old diary under a loose floorboard at the Old Sawmill Guest Ranch in Nemo, South Dakota. The cousins are filled with questions about what happened to Sophia, the diary's owner, and what happened to the gold coin that she was meant to give to her father? Could all their discoveries be clues to help answer the historic Black Hills puzzle and reveal where Custer hid his last payroll? With only a few days to their vacation and the threat of snow, the Double Cousins race against the clock in their most recent mystery. Recommended for ages 8 to 12 years.