Jim Leonard Jr.'s "The Diviners"

In the 1930's, Zion, Indiana has a populations of 40.  Drought has made the Depression-era town bone dry.  Buddy, a mentally challenged teenager, claims that he can sense when water is near.  He is searching or "divining" for water for local farmer, Basil.  Basil's wife, however, doesn't believe that he will find it.  See en.wikipedia.org/wiki/The_Diviners_(play).

C. C. Showers, a stranger from out of town, arrives and immediate takes to Buddy.  C.C. becomes Buddy's mentor.  C.C. also attracts the eye of young Jennie Mae.

The dry goods owner in town, Norma, who cleans her store to the tune of "Rock of Ages", wants a church revival.  The local diner wants the local church rebuilt.  All they need is a preacher.

It is revealed that C.C. has a secret:  he is a preacher who comes from a long line of Kentucky pastors.  The town tries to persuade C.C. to fill the pulpit at their church, but, after a crisis of faith, he is "determined not to do what he does best" (http://www.samuelfrench.com/p/693/diviners-the).

In the meantime, C.C. tries to persuade Buddy to take a bath, but Buddy is deathly afraid of water, after the drowning death of his mother.  Finally, one day C.C. manages to convince Buddy to bathe in the river, to the strains of "Shall We Gather at the River".  However, the townspeople see the preacher "dunking" the teenager in the river and mistake it for a baptism.  They descend upon the scene and tragedy ensues with the accidental drowning of Buddy.

Even so, despite the tragedy, it is "Amazing Grace" which plays at Buddy's funeral, pointing to the hope the townspeople hold on to.

http://fcnp.com/2010/12/13/falls-church-highs-technically-superb-qthe-divinersq/