Dr. Macphail
Dr. Macphail is a forty-year-old Scottish doctor and WWI veteran with red hair and freckles. He looks forward to working for twelve months in Apia, American Samoa, but gets waylaid at the port of Pago Pago for two weeks because one of the ship's crew members has measles. He and his wife befriend a missionary couple on their ship. The doctor tolerates the righteousness of Davidson and his wife, but often judges them and sometimes replies with sarcasm when they say disagreeable things. Dr. Macphail particularly disagrees with Mr. Davidson's treatment of fellow traveler Sadie Thomson, an alleged prostitute. Although his default position is to stay out of other people's business, Macphail advocates on the young woman's behalf to both the governor of Pago Pago and to Davidson.
Mrs. Macphail
Mrs. Macphail is the wife of Dr. Macphail. She is a timid woman used to do as her husband bids her. She gets along with the Davidsons much better than her husband does and she spends most of her time with Mrs. Davidson. Dr. Macphail often uses her to communicate with the Davidsons indirectly.
Davidson
Reverend Davidson is an American Christian missionary. He is tall, has fiery eyes, and speaks in a loud voice. He is extremely pious and considers it to be his life’s aim to bring everyone he encounters to the right path. One of his greatest achievements is installing a sense of sin in the natives of his district north of Apia, who in his eyes regularly broke the ten commandments and lead an immoral life before being taught to feel shame and fear. The missionary is enraged to find out that one of the occupants of the house they are renting rooms in is a prostitute. Determined to bring Miss Thompson to righteousness, Davidson convinces the island's governor to order her deported on the next boat to San Francisco, where she will face a three-year prison term. After breaking Miss Thompson's defiant spirit and getting her to repent, Davidson becomes obsessive, spending most of his time praying with her. However, the night before she is supposed to leave, the missionary leaves her room and commits suicide on the beach.
Mrs. Davidson
Mr. Davidson's wife is also a missionary. She is small, wears pince-nez, and speaks in a high voice that grates on Dr. Macphail. She often praises her husband, his achievements and determination, and denounces the Samoan natives and their immoral lifestyle. Mrs. Davidson also expresses concern about her husband's health, and keeps repeating that he will wear himself out in his obsessive quest to rescue lost souls.
Miss Thomson
Miss Sadie Thomson is a twenty-seven-year-old woman who gets stuck on the island with the Macphails and the Davidsons. She dresses in an all-white, ostentatious outfit, and rents out a room downstairs in Mr. Horn's house, where she has sex with sailors for money. When Davidson realizes she must have come from the Honolulu red-light district, he is determined to disrupt her business and make her suffer. Sadie is distraught to learn he has made it so that she will have to return to San Francisco and serve the jail term waiting for her there. After she is unable to persuade the missionary to let her go to Sydney instead of San Francisco, she breaks down and repents. She spends her days crying, reading the Bible, and praying with the missionary. During the night before her departure, the missionary kills himself and she returns to her old self. When Macphail confronts her about her callousness towards Mrs. Davidson, whose husband has just died, Sadie exclaims that all men are the same, they are all pigs.
Mr. Horn
Mr. Horn is a half-white, half-Samoan trader who lives in Pago Pago and has rooms to rent to the stranded couples. When Davidson learns that Sadie Thomson is a prostitute, he makes Mr. Horn forbid her to bring her customers in. Mr. Horn later leads Dr. Macphail to the missionary's dead body.
The Governor
The Governor is an American man stationed as a legal authority at Pago Pago. After receiving threats from Mr. Davidson, who promised to complain about him in Washington unless he would yield to his request, the governor orders Miss Thomson to leave on the next ship to San Francisco. The governor receives another visit from Dr. Macphail, who comes to plead for Sadie, but he turns the doctor down, afraid the meddlesome missionary will cause problems for him.
Fred Ohlson
Fred Ohlson is a Danish trader who lived in Samoa before the Davidsons arrived. When Ohlson would not repent for his wealth-hoarding, adultery, and drunkenness, Davidson spent two years doggedly ruining his reputation and social standing until the man lost everything and became desperate for help.
