Kevin Boyle's Arc of Justice depicts the racial turmoil in Detroit in 1925 through the story of Dr. Ossian Sweet, an African-American physician who faces murder charges after trying to defend his home in an all-white neighborhood from mob violence. The grandson of a slave, Ossian moves northward during the Great Migration to get his education at Wilberforce and Howard Universities. After graduating Howard's medical school, Ossian sets up practice and residence in Black Bottom, Detroit's crumbling black and immigrant neighborhood. After marrying his wife, Gladys, the couple buy a home in an all-white neighborhood, Garland Avenue, on the city's west side. Fearing a mob attack, as had happened to other black homeowners who dared cross Detroit's color line, Ossian asks his brothers and a few friends to stay with him and Gladys on their first night in the house. Ossian supplies the men with a variety of guns and the group anxiously wait out the night. When a mob of angry white neighbors attacks Ossian's house, pelting it with stones in order to "put out" (168) the black couple, Ossian's friends open fire on the mob, killing one man and injuring another.

The newly formed National Association for the Advancement of Colored People, or NAACP, agrees to provide defense for Ossian and the others. The NAACP hires"the Great Defender" (233), Clarence Darrow, "the most brilliant defense attorney in the country" (228) and a champion for working class rights. James Weldon Johnson, the NAACP's secretary, hopes that this hire will garner enough publicity to attract both the attention and support of black and progressive white Americans in the NAACP's fight against residential segregation. While the prosecution leans on disproving the existence of a mob and showing that the gun shots were unprovoked, the defense relies on demonstrating the obvious racial bias in both the arrests and accusations. Darrow stacks the jury with white men, all of whom are "related to immigrants" (267). He forces a mistrial by adopting a conversational tone with the jurors as he sets them in opposition to Detroit's burgeoning Ku Klux Klan, who hope to preserve "one hundred percent Americanism" (280) in their city and country. Following the mistrial, Darrow returns to defend Henry Sweet, Ossian's brother, made to stand on trial for the murder by himself. Henry's verdict of "not guilty" (336) ensures the acquittal of Ossian, Gladys, and each of the other eight men accused.

As the trial unfolds, it's clear that the case doesn't "pivot on facts of law" (217). Rather, it hinges heavily on both Detroit's political climate and race relations in the United States following the Great Migration. Despite"hundreds of years of precedent" (186) that legally grant a person the right to defend themselves and their property if they believe they're in "imminent danger" (186), as black citizens, Ossian and the others must stand on trial. Boyle traces Ossian's family history back to his grandparents, both slaves until the end of the Civil War, to show the oppression and violence suffered by black Americans since they were brought to the United States as slaves. Boyle also shows the fractures in Detroit's white community between native-born Americans, some of whom join the twenty-thousand strong KKK, and immigrants and their families. Among them are Frank Murphy, the Irish Catholic judge who presides over Ossian's case, and Johnny Smith, who rallies the immigrant vote by getting them to feel "the humiliation, frustration, and fury" (251) of being considered less-than white by the Klan. With Murphy and Smith in positions of political power, immigrants and black Detroiters feel some progress made towards creating a less segregated city. Thus, the mistrial and subsequent verdict and acquittals mark small victories in undoing some of the injustices of structural racism.