In the 1930's Mongol Tunga Khan is terrorizing the people of the Chinese border. In the area is an American mission headed by prim, iron-willed Agatha Andrews. Assisting her are admiring Jane Argent, young Emma Clark, ineffectual teacher Charles Pether, and his frightened, pregnant wife, Florrie. At first glad to hear that a Dr. Cartwright will soon be joining them, Agatha is displeased when the doctor turns out to be a cynical, worldly woman. The conflict between the two women is sharpened with the arrival of cholera-bearing refugees from the nearby ravaged British mission headed by Miss Binns, and matters are not helped by Agatha's refusal to provide the funds necessary to send Florrie to a hospital. When the Chinese soldiers protecting the area depart, Pether, with new courage, sets out to seek news but is killed. Tunga Khan and his forces storm into the mission as Florrie's labor pains begin. To pacify the invaders, Dr. Cartwright agrees to give herself to the warlord once she has delivered the baby; then, after the child is born, she uses her new power over Tunga Khan to provide for the pressing needs of the women and child. Miss Andrews, hysterically losing control, condemns Dr. Cartwright as a wanton and lustful woman, but the others understand her sacrifice. Dr. Cartwright then gets Tunga Khan's permission for the women to leave the mission. After their departure, she secretly poisons some wine and shares a toast with the warlord.