A nun helps a doctor clean up the ghetto in which he lives.

John Carpenter, a young doctor operating a free clinic in a ghetto, looks with apprehension on the arrival of three nuns who have been granted special dispensation to wear laymen's clothing and help him with his work. Gradually gaining the respect of the community are: Sister Michelle, a speech therapist, who is able to help Julio Hernandez, the leader of a gang of juvenile delinquents, and who also works with an autistic child; Sister Irene, a Negro, who demonstrates her own sense of ghetto wisdom; and Sister Barbara, who becomes involved in protesting the unfair prices that a local food market charges the residents. Dr. Carpenter, who is unaware that the women are nuns, falls in love with Sister Michelle, but she gently rebuffs him and becomes even more involved in community affairs. Despite interference from her superior, Bishop Finley, Sister Michelle organizes a block party to bring the black and Puerto Rican elements of the community together. At the party, "The Banker," a local black gangster, slaps Sister Irene for meddling in his business affairs, but Dr. Carpenter knocks the gangster down. Later, Sister Michelle is nearly raped by Julio Hernandez, and again Dr. Carpenter comes to the rescue. Meanwhile, Sister Barbara, who has been picketing the market, is arrested, and Mother Joseph, the nun in charge of the convent, orders all three women to leave the project. Sister Michelle, who is now in love with Carpenter, must choose between him and the Church.