John Howard Griffin is a middle-aged newspaper columnist and former rancher living in Texas in 1959. Writing in his diary, Griffin, a white man, recounts how he hit upon the startling idea to change his skin color and attempt to experience life as a black man. Deeply preoccupied by the growing racial conflict in the United States, Griffin reads a troubling report about the rise in the suicide rate among American Negroes. He realizes that, as a white man, it is virtually impossible for him to understand what life is like for blacks, especially in the South. Committed to the social cause of black Americans and desperate to understand their situation, Griffin thinks that his only hope of obtaining insight is to transform himself into one of them—an idea that frightens him as much as it attracts him.
Griffin travels to Fort Worth to discuss his idea with his friend George Levitan, the editor of Sepia, a magazine devoted to Negro issues. He tells Levitan that he wants to change his skin color and become a black man for a short period of time, in an attempt to bridge the racial divide that prevents blacks and whites from understanding one another. Griffin hopes that Levitan will fund his project in exchange for being allowed to publish excerpts from the book he plans to write about his experience. Levitan is shocked by the idea, as is Adele Jackson, his editorial director. They warn him against the social repercussions to which he will subject himself if he goes through with his scheme. They say he risks everything from his family being ostracized by the community to outright violence perpetrated by racist organizations such as the Ku Klux Klan. Despite the risks, Griffin is insistent that he wants to go through with his plan, and Levitan finally agrees to fund the transformation.
Griffin returns home, where he tells his wife about his idea to temporarily change his skin color. Though she is shocked by his plan, she recognizes the strength of his convictions, and she agrees to care for their three children while he is living out his experiment. As night falls, Griffin sits in his office in the barn, fighting against a powerful sense of fear.
He decides that after he undergoes the change in skin color, he will keep the same identity: he will not pretend to be anyone other than John Howard Griffin, the writer. This will allow him to gauge the responses of whites, and to see whether they will be able to treat him as anything other than an anonymous black man. He suspects that they will not. Griffin informs the FBI about his plan. One FBI agent is skeptical and warns him that if he becomes a Negro, he can only expect to be treated as a Negro.
Griffin travels to New Orleans, where he will undergo dermatological treatment to change his skin color. He wanders contemplatively through the white French Quarter section of town, observing the high standard of living among New Orleans whites, and wonders what he will find in the black part of town, where he will live after the treatment. He remembers a time in his life when he was temporarily blind, and thinks that, in a sense, his eyesight is still faulty, because he cannot see the city with the eyes of a black man.
Griffin treats himself to an opulent candlelit dinner in an outdoor restaurant, thinking of how he would be treated as a black man in a restaurant such as this. He calls a friend, and tells him that he is in New Orleans on a secret assignment. The friend offers to let him stay at his house while he is in New Orleans, and Griffin decides to do so, at least while he is undergoing the treatment.