The Testaments braids together three separate first-person testimonies, each of which corresponds to one of the novel’s three narrators. The first narrator, Aunt Lydia, composes her account in a manuscript known as “The Ardua Hall Holograph.” The other two narrators, Agnes and Daisy, each give spoken accounts, which appear in the novel as transcripts of witness testimonies. Each of the three narrators tells the story her role in a conspiracy to topple the patriarchal and theocratic regime of the Republic of Gilead.

In “The Ardua Hall Holograph,” Aunt Lydia charts her rise to power within Gilead. Prior to the coup that brought down the United States government, Aunt Lydia had an accomplished career as a judge. She tells of her arrest and her experience of being held in a stadium where she watched as members of the new regime executed other professional women. As the days passed, Aunt Lydia saw that women were replacing men as the executioners.

One night, men came for Aunt Lydia and escorted her to a man named Commander Judd. He asked her if she would cooperate with the regime. When she hesitated, he dispatched her to several days of solitary confinement, after which she agreed to cooperate. Despite knowing that she would have to participate in an execution of other women, Aunt Lydia decided to do whatever necessary to survive and take down Gilead from within. Alongside three other women—Elizabeth, Helena, and Vidala—she became one of the Founders of the Aunts. The Founders were responsible for drafting and enforcing the laws that governed all women in Gilead. Aunt Lydia quickly gained dominance over the other Founders and sought ways to play the three against each other. In the time since Gilead’s founding, Aunt Lydia has established a vast network of surveillance equipment to collect evidence of others’ indiscretions.

As Aunt Lydia composes her manuscript, she is actively engaged in tracking the whereabouts of “Baby Nicole,” a child famously smuggled out of Gilead and into Canada many years earlier by her Handmaid mother. Baby Nicole’s whereabouts remain concealed by operatives of an anti-Gilead resistance group called Mayday.

The novel’s other two narratives feature two young women: one who grew up in Gilead and one who grew up in Canada. These women become involved in a plot spearheaded by Aunt Lydia to topple Gilead.

Agnes Jemima grew up in a privileged Gilead family. Her happy childhood ended abruptly when her mother, Tabitha, died and her emotionally remote father married a cruel widow named Paula. Agnes was anxious about Gilead’s treatment of women from an early age. Her fears were confirmed when she witnessed the horrific death in childbirth of her family’s Handmaid. When Agnes reached the age of thirteen, Paula sought to marry her off to Commander Judd. One of Agnes’s school friends, Becka, attempted suicide to escape her own marriage, and Agnes contemplated a similar course. But one day, Aunt Lydia paid her a visit and suggested she avoid marriage by taking refuge among the Aunts.

Agnes found a way to maneuver around Paula and successfully pledge as a Supplicant. Once she arrived safely at Ardua Hall, Agnes was reunited with Becka, who had also pledged. As part of her training, Agnes learned to read and write, two activities forbidden to all women except for Aunts. During this period, she learned that much of Gilead’s official theology contradicted the Bible. She also received folders containing top-secret information about corruption among Gilead’s elite from an anonymous source. Agnes realized that the Aunts got their power from these secrets, and she hungered for more access to that power.

The third narrator, Daisy, grew up in Toronto, Canada. Her parents, Melanie and Neil, owned and operated a used clothing store. One day, against her parents’ wishes, Daisy attended a protest against human rights violations in Gilead. When the protest turned violent, she escaped with the help of Ada, a mysterious middle-aged woman who was friends with her mother. That night, Daisy’s image appeared on the TV news, scaring her parents.

Not long after, on Daisy’s sixteenth birthday, her parents were killed in a car bombing outside their store. Ada picked Daisy up from school and broke the news. With help from some colleagues, Ada set Daisy up in a safehouse on the edge of town. Ada and her colleagues explained that Melanie and Neil weren’t Daisy’s real parents. Instead, they were Mayday operatives selected to look after her while her real mother remained in hiding. Ada also explained that Daisy was the famous “Baby Nicole” and had been smuggled out of Gilead by her mother, a runaway Handmaid.

Ada and her colleagues explained their commitment to undermine Gilead and how they had a source inside the regime who wanted to send top-secret documents that would help topple the government. However, the deaths of Melanie and Neil had closed their channel of communication with the source, and their only backup plan was to send Daisy into Gilead to retrieve the documents herself. Daisy snuck into Gilead by pretending to let two missionaries, known as Pearl Girls, convert her.

The three women’s lives converged when Daisy arrived at Ardua Hall and Aunt Lydia placed her in Agnes’s apartment. In due time, Aunt Lydia revealed herself to Daisy as the source and implanted a minuscule document called a “microdot” containing vast amounts of information about corruption in Gilead into Daisy’s arm. She also revealed to Agnes and Daisy that they were sisters. Claiming that she wanted to reform the spiritually rotten core of Gilead, Aunt Lydia enlisted both young women, along with Becka, in a plot to help Daisy escape with her top-secret document cache. Despite a series of complications, Agnes and Daisy successfully escaped to Canada. The incendiary documents immediately hit Canadian media and set the fall of Gilead in motion.

The novel’s final section, which takes place far in the future in the year 2197, features a historian named Professor Pieixoto speaking about the written and spoken testimonies that constitute the rest of the book.