Arrowsmith has strict instructions from Gottlieb to employ the scientific method in his efforts, conducting a blind study by administering the serum to one-half his patients and a placebo injection to the other. Upon learning of this, the West Indies governor, Sir Robert Fairland, refuses to allow him to proceed. Seeking to break the impasse, black Dr. Oliver Marchand suggests Arrowsmith conduct his experiment in a backwater community on a neighboring island where the infection is rampant. Arrowsmith agrees, insisting Leona stay behind for her own protection. The study begins. Among those seeking an inoculation of Arrowsmith's serum is Mrs. Joyce Lanyon, a New Yorker stranded on the island. They are attracted to each other, though their subsequent affair is only hinted at obliquely.