Blood of the Prodigal by Paul L. Gaus
This mystery is set in Ohio among the Amish. A Bishop's grandson, Jeremiah, disappears. The bishop turns to a local "English" professor to help locate the boy, as he really doesn't want the whole matter to go public by contacting authorities. He feels that the grandson is with his father, who was banished from the community 10 years earlier.
Eventually, the Bishop's Son is found.....dead......shot to death near the Bishop's farm...but still no sign of his grandson.
With no other recourse, the case does go public as the professor works with the sheriff and his deputy to solve the murder and find the grandson.