Kidnapped! (Doc and Johnny's Old West Mysteries Book 4) by David Drake

Book Four: 10 to 15 year old readers. Kidnapped: Johnny’s Aunt Bea and the banker’s wife are kidnapped for a large ransom during the week in early spring when Abbot comes to visit. Johnny, Jerry and Abbot take the lead in solving the mysteries of who is behind the abduction and where they are being held. Johnny refuses to pay the ransom so they have to find ways of pushing back deadlines to give them more time. They encounter problems with an old man and a rifle, an old mine that is prone to collapsing, and a long abandoned mill. There is action, mystery, excitement, and the developing friendship among the three boys who call themselves the tres amigos inteligente (the three smart friends).