Arc of Justice by Kevin Boyle is a book about race relations during the Roaring Twenties. Ossian Sweet, sent away from his family home in Bartow, Florida, at the age of thirteen, buys a house in an all-white neighborhood in Detroit. Sweet had spent his summers working in Detroit while putting himself through college - first Wilberforce University in Xenia, Ohio and then Howard University Medical School in Washington, D.C. His parents send him away from the Jim Crow South to Wilberforce where he completes high school and college. They worry about his safety and want him to have a better life. The promised scholarship does not materialize at Wilberforce, however, so at just thirteen years of age, Sweet works odd jobs to pay his own way. He is attracted to Detroit's high paying auto-industry, thinking he will be able to secure a good job that will help him pay his expenses at Wilberforce. He takes whatever menial jobs he can find.

Through Ossian Sweet, the reader is exposed to the situation of the African-American population in 1920s Detroit. Sweet and his wife, Gladys, live with her parents after they are married and after spending a year overseas. They save for the down payment on a house and try to find an area to where they can relocate. Color lines are drawn to keep the African-Americans in the Black Bottom ghetto area, with a few other places available. They buy a house on Garland Avenue in Detroit, an all-white working class area. The couple can't get a bank mortgage because of the color of their skin, so they arrange to pay the sellers a monthly payment plus eighteen percent interest. Before they move in, there are incidents in other all-white neighborhoods in which blacks have taken residence. Sweet arranges to have several other men stay with him and his wife for the first few days in the house and he possesses guns for protection. The neighborhood organizes a plan to expel Sweet and his wife from the neighborhood through the formation of the Waterworks Park Improvement Association. The group will use violence if it gets to that point. On the second night, the mob pelts the house with stones, breaking a window. Henry Sweet opens fire and kills a white man named Leon Breiner. All of the people in the house are arrested, including Gladys. Gladys is later released, but the others stand trial.

The NAACP comes to the family's aid with the provision of a big-name legal defense team of Clarence Darrow and Arthur Garfield Hays. This event happens in the early days of the NAACP and becomes a national rallying cause for the organization in its fight against housing discrimination. The organization provides the high-priced, big-name, white defense lawyers to chip away at the cover-up and the lies of the witnesses who have been coached by certain police officers and by the Waterworks Park Improvement Association people. Detroit at this time is a Klan stronghold, and the events unfold against the backdrop of the Klan fighting for election to city offices.

Arc of Justice is the powerful story of the blacks' fight for equal rights and their willingness to stand up for their rights. Ossian Sweet's struggle represents that of many other blacks during the period of racial prejudice and tension.