Caravan Courage by William Black

The fearless and famous Dory McLee and her friend Evan Henson are back and facing another challenge. Jed Coburn, owner of a caravan freight wagon firm, has been murdered by disgruntled worker Flint Mattox. Evan is out to help the Coburn family after they saved the life of his brother. What will it take for Dory and Evan to capture the evil Mattox?