David Treadup may well be Hersey's most convincing character. He is, as Hersey has admitted, a composite of several missionaries whom he knew, including his father, Roscoe Monroe Hersey, to whom he has dedicated the novel. Unlike Treadup, Roscoe Hersey was a mild person, although totally dedicated. David Treadup, in contrast, pursues his work with boundless energy and ferocity. Nothing must be allowed to interfere with his work.

Over six feet tall and rugged in proportion, he tirelessly covers a circuit of many villages on his Indian motorcycle, giving his science lectures. Intelligent, he acquires early in life a skepticism which never quite disappears, even during that time in his life when he is most devout. His open mind is a result of a teacher he had during high school, Absalom Carter, a physics teacher remarkable for his inventiveness in the classroom, who helps guide his reading habits...