Why Didn't They Ask Evans?

When vicar's son Bobby Jones and Dr. Alwyn Thomas play a round of golf, Bobby slices his ball over the edge of a cliff. His ball is lost, but on the rocks below he finds the crumpled body of a dying man. With his final breath the man opens his eyes and gasps, 'Why didn't they ask Evans?' Becoming convinced the man's death may have been a murder, Bobby and his socialite friend Lady Frances "Frankie" Derwent set about solving the mystery.