In April, Detective Izzy Jaynes visits Lieutenant Lewis Warwick, who shows her an anonymous letter addressed to him and Chief Patmore. Signed by “Bill Wilson,” the note invokes the Blackstone Rule, claims that “the innocent should be punished for the needless death of an innocent,” and promises to kill thirteen innocents and one guilty person as an act of “atonement.” Izzy and Warwick quickly connect the letter to Alan Duffrey, a bank officer who was convicted as a sex offender, murdered in prison, and later may have been framed by his rival Cary Tolliver. Because the letter seems both irrational and deliberate, Warwick decides not to dismiss it as a crank threat and assigns Izzy and Tom Atta to question Tolliver and trace Duffrey’s associates.

Izzy then meets Holly Gibney for lunch in Dingley Park. Their friendship, strengthened by past shared trauma, allows Izzy to show Holly the letter and ask for her opinion. Holly agrees that the Duffrey case is the most likely trigger and suggests the writer may be educated, religious, or connected to AA or NA, since “Bill Wilson” was AA’s founder. The scene also deepens Holly’s personal subplot: Barbara Robinson later calls with ecstatic news that she has won tickets and backstage passes to see Sista Bessie at the Mingo Auditorium, and Holly agrees to go with her despite Holly’s uneasy memories of that venue.

Back in her office, Holly cannot stop thinking about the note. Although she tells herself the case is Izzy’s, not hers, she analyzes the language and concludes the writer is intelligent, white-collar, and careful with punctuation and business-style formatting. Holly emails Izzy these deductions, adds the useful observation that the writer misspelled Lewis Warwick’s first name as “Louis,” and suggests that recovery meetings might offer a slim lead if the alias points to AA or NA. Afterward, Holly notices she may have double-booked the same May 31 evening for Barbara’s concert and a Kate McKay appearance at the Mingo Auditorium, hinting that separate plotlines may be converging.

Meanwhile, Izzy and Tom visit dying Cary Tolliver at Kiner Memorial. A nurse openly despises Tolliver, and the detectives find him drugged, filthy, and self-pitying in the solarium. When shown the “Bill Wilson” letter, Tolliver assumes he might be the one guilty target but offers little insight into the sender. Instead, he confirms in bitter detail that he framed Duffrey after losing a promotion to him, planted child pornography in Duffrey’s house and computer, and confessed only after receiving a terminal diagnosis. He blames the ADA for ignoring his confession, insists he never meant Duffrey to die, and gives the detectives names from the bank who knew Duffrey well. Tom rejects Tolliver’s pleas for sympathy, and the detectives leave convinced that whatever remorse Tolliver feels does not erase the damage he caused.

In May, the chapter shifts to Trig and reveals that the threat is real. Having already sent the warning letter to police, Trig drives to a trailhead near Upriver with a revolver, a backpack, and slips of paper bearing names. He tells himself that if no one appears alone, he can still stop, but when a middle-aged woman walking a Standard Poodle approaches, he uses a trail map to lure her close. Trig shoots her in the head, drags her body into the woods, leaves one of the prepared name slips in her hand, and flees. Shaken but not remorseful enough to stop, Trig realizes he has crossed the line for good and has begun the campaign of murder he calls atonement.