The Secret of Skull Creek Caves (History Mystery for Kidz Book 4)

Set against the backdrop of Arizona Statehood, Stephanie and Amy Hutchins, fraternal twins and eleven-year-old girls who live in Arizona Territory in 1912, have stumbled onto a mystery and are determined to solve it.
When they find out that two of their classmates, who are orphans, are being beaten by their older brother who is forcing them into cattle rustling, the girls try to persuade their parents to hide the boys and help them escape their brother's control. But before the family can help, the brothers disappear. Where have they gone? The family looks everywhere to no avail.
Can the girls find the boys before their brother finds them? Can they help keep the brothers safe until the circuit judge comes to town and lets them be adopted? It's a race against time.