Two decades later, when the events of “Go Set a Watchman” take place, white dominance has been shaken. Blacks are demanding the vote and attacking racial segregation. Finch’s previous unflappable patrician calm now gives way to defensive anxiety. He defends segregationist propaganda with titles like “The Black Plague.” He derides the National Association for the Advancement of Colored People (N.A.A.C.P.), especially its lawyers. He rails against the prospect of blacks leaving their “place.” “Do you want Negroes by the carload in our schools and ­churches and theaters?” he asks his daughter, Jean Louise (also known affectionately as Scout). “Do you want them in our world?” He veers between expressing condescension — “Honey, you do not seem to understand that the Negroes down here are still in their childhood as a people” — and expressing contempt: “Can you blame the South for wanting to resist an invasion by people who are apparently so ashamed of their race they want to get rid of it?”

The audience for these questions, Jean Louise, the grown-up Scout, is bereft of her beloved childhood companions. Jem, her brother, has suffered the fate of their mother: death at an early age from a sudden heart attack. Her mysterious neighbor, Boo Radley, is gone; and Dill, Scout and Jem’s irrepressible summertime chum (a character modeled on Lee’s longtime friend Truman Capote), is largely absent too.

The most striking new presence is Henry Clinton, a hard-working young lawyer in Atticus’s practice who hopes to marry Jean Louise. She appears to be on the verge of succumbing when she learns to her dismay that Henry, like Atticus, is a member of the Maycomb County Citizens’ Council. Established in the aftermath of Brown v. Board of Education, White Citizens’ Councils were tonier alternatives to the Klan. They were designed to be respectable organizations that would enable businessmen and professionals to thwart racial desegregation.

Henry figures in two of the most memorable scenes in the novel. In one, he climbs a water tower to save Jean Louise. Still ignorant about sex as a sixth grader, she believes she is pregnant because a boy at school put his tongue in her mouth. She considers jumping off the water tower to commit suicide to spare her family disgrace. In another scene, Henry escorts Jean Louise to the high school prom. She is wearing falsies that stray. “Her right false bosom was in the center of her chest, and the other was nearly under her left armpit.” He hugs her close to prevent others from seeing what has happened, comforts her outside of the school gymnasium, and throws the falsies away. When they land on a sign honoring students who have joined the armed forces after graduation, the school’s outraged principal demands that the guilty party turn herself in. Henry, with Atticus’s counsel, concocts a scheme in which each of the girls at the school writes a note saying the offending falsies look like her own, ensuring that no one bears the full weight of the principal’s anger.

Although “Go Set a Watchman” sporadically generates the literary force that has buoyed “To Kill a Mockingbird” for over half a century, the new novel is not nearly as gripping as the courtroom drama and coming-of-age story it eventually became. The first hundred pages are largely desultory, though they do create a sense of anticipation. Then Lee begins to introduce the reader to Jean Louise’s discovery that Atticus and Henry have joined the White Citizens’ Council. Her disappointment, which develops into anger, suggests an opportunity to explore a dense, rich, complicated subject: How should you deal with someone who has loved you unstintingly when you find out that this same person harbors ugly, dangerous social prejudices?