An unnamed narrator says that the story begins in a room she’ll never see on a hot summer night in Baltimore, Maryland in 1939. A young, pretty woman named Christine is screaming and sweating on a hospital bed surrounded by nurses. Christine gives birth to a stillborn daughter, although Christine is too heavily medicated to comprehend what is happening. A doctor walks out to where Christine’s father is anxiously waiting for news. The doctor tells the man that not only was Christine’s daughter stillborn, but that Christine will never be able to safely carry a baby to term. Distraught, the man says that Christine is his only child and that he and his wife had been looking forward to having grandchildren in the house. The doctor leans down and tells the man that there is a woman in Memphis who can help.
In the present day, Avery Stafford is gearing herself up for a public appearance at a nursing home with her father, Senator Wells Stafford. The two are in a limo alone together as they pull up to the nursing home. Avery thinks about why she’s come back home to Aiken, South Carolina: her father has been diagnosed with cancer and might have to step down from his office in the U.S. Senate if his condition worsens, so Avery has been called home to be groomed to take his spot in Congress. Unfortunately, this also means that she is living several hours away from her fiancé, Elliot. In the nursing home, Avery and Wells and smile and take pictures with their political supporters. While they sit up on the stage and listen to the life story of the woman whose 100th birthday they’re celebrating, Avery finds herself watching an elderly woman who is standing alone outside. When the audience inside sings “Happy Birthday,” the old woman slowly turns around and starts walking back to the facility. Avery is clearly distracted by the sight of the woman, so her father’s assistant, Leslie, tells her to focus so the cameras don’t catch her looking distracted. Suddenly, the old woman Avery was watching grabs Avery’s wrist and says, “Fern?” Avery is stunned, but a nurse quickly comes up and tries to the lead the woman—whom she calls May Crandall—away.
Back at her parents’ house, Avery calls Elliot and gets ready to take a family Christmas picture even though it’s July—Avery’s mother, Honeybee Stafford, is worried that Wells’s hair will thin due to his new cancer treatment. Avery plays around with her sister Allison’s daughter Courtney until she gets a phone call from the nursing home she visited earlier. The nurse on the phone tells Avery that they found May with a dragonfly bracelet she slipped off Avery’s wrist at the birthday party. Avery loves the bracelet because it belonged to her grandma, Judy Stafford, before Judy had to be put into the memory care unit of an upscale nursing home. Avery decides to go get the bracelet herself instead of sending Leslie’s intern, Ian, because she also wants to know more about May. At the nursing home, Avery walks into May’s room and notices an old picture of a couple. The woman in the picture bears a striking resemblance to Judy, so Avery takes a picture of it. Suddenly, May walks in and strikes up a conversation with Avery. May mentions that she knows Judy Stafford from her bridge club but won’t answer any questions about the picture. Avery goes to visit Judy and ask her about May and the picture. When Avery shows Judy the picture, Judy touches it lightly and says “Queenie.” Judy also cryptically tells Avery that nobody can ever know about the Arcadia but doesn’t explain what this means.
Avery is unable to shake the feeling that her grandmother is somehow connected to May Crandall, so she decides to go through Judy’s account books and papers. In one of Judy’s notebooks, Avery finds the phone number for someone named Trent Turner. Avery doesn’t recognize the name, but she calls and finds out Trent works in real estate on Edisto Island, where Judy owns a beach house. After a little more research, Avery finds out Trent is actually Trent Turner Sr., but that he died six months before and left the business to his grandson, Trent Turner III. Trent Turner III talks to Avery on the phone and says he has a packet of papers that his grandfather wanted Judy to have, but he refuses to give the files to Avery. Determined to know what’s going on, Avery visits Trent in person, but he still refuses to give her the papers. Avery goes to her grandmother’s cottage and finds an old typewriter, pulls out the tape, and deciphers the last few lines of the last letter that was typed up on it. The lines indicate that Judy was trying to learn more about the Tennessee Children’s Home Society (TCHS). Confused and worried that her family has a dark secret, Avery calls Trent and demands answers. Reluctantly, Trent agrees to give Avery the papers, which turns out to be the record of the adoption of Shad Arthur Foss. Avery is still confused, so Trent suggests they look through his grandfather’s office, which is full of files about the TCHS. Just then, however, Trent’s son, Jonah, comes out of his bedroom and Avery leaves. She feels drawn to both Trent and Jonah but pushes this out of her mind with thoughts of Elliot.
The next day, Avery and Trent go into Trent’s grandfather’s office. On the way, Avery reads an article about Georgia Tann, who ran the TCHS and abused many of the children who passed through the system—many of whom were kidnapped from poor families. In the office, Trent learns that his grandfather was one of these children, but Avery is left with more questions than answers. She decides to go back to May and Trent goes with her. May tells Trent that she knew his grandfather because the two of them were at the same orphanage in the TCHS together, back when Trent Turner Jr. was called Stevie. May tells Avery that Judy was simply writing an article about the TCHS, but Avery doesn’t believe her. In light of the possibility that her family has a dark secret, Avery begins reevaluating her entire life, including her engagement to the passionless Elliot.
Trent calls Avery one day and asks her to lunch. On her way to meet him, Avery sees a taxi sitting in the driveway of Judy’s house and decides to check it out. The driver says there has been a standing appointment for Judy to be picked up every Thursday for years. Confused, Avery asks Trent to go with her to find out where the taxi goes. The taxi drops them off at a house in Augusta. Trent and Avery knock on the door and walk in when nobody answers. Inside, Avery sees an old picture of her grandmother with three other women, all wearing matching dragonfly bracelets. They hear a man outside and go out to meet them. The man brings them to his mother, Hootsie, who cares for the house. Hootsie gives Avery the beginning of a memoir that Judy was writing. In it, Judy reveals that she is the daughter of Queenie and Briny Foss—and that she was kidnapped and sold to Christine’s father to replace her stillborn daughter. The other women in the picture in the cottage are Judy’s siblings, one of whom is May.
Back in 1939, Rill Foss is 12 years old and struggling to take care of her younger siblings—Camellia, Lark, Fern, and Gabion—by herself after her parents, Queenie and Briny, go to the hospital so that Queenie can deliver her twins. A family friend, Old Zede, returns from the hospital to let Rill know the twins were stillborn and to drop off Silas, who will care for the siblings until Queenie and Briny can come back. After Zede leaves, a group of policemen board the family’s shanty boat and demand that Rill and her siblings go with them to see their parents. Rill agrees to go and, using her eyes, tries to tell Silas to go tell Zede. The policemen bring the siblings into Memphis, near where their boat is tied up. They are handed over to Georgia Tann, who already has two children that she calls Stevie and Sherry with her. The seven children are brought to an orphanage run by Ida Murphy with the help of Mrs. Pulnik. At the orphanage, Tann gives Rill and her siblings new names: May, Iris, Bonnie, Beth, and Robby Weathers. They are sent to the basement, where they’ll sleep until Murphy thinks they deserve to move upstairs. Although the five Foss children are terrified, they are happy to be together. In the middle of the night, the groundskeeper, Mr. Riggs, comes in and leaves peppermints on their pillows.
A short time later, Rill, Lark, Fern, and Gabion (the four Foss children who have curly blond hair) are dressed up and brought to a viewing for prospective adopters. The three younger children catch the attention of couples rather quickly, but Rill is left mostly to herself and tries to keep her eye on her little sisters and brother. At the end of the viewing, however, the couple who has been playing with Gabion don’t want to let him go. Georgia Tann allows them to pay for him on the spot despite Rill’s attempt to tell them he already has parents. Rill is shocked by what happened and is silent on the way back to the orphanage. When they get back, Rill immediately searches for Camellia and finds her crying by a bush. Rill asks what happened, but Camellia won’t talk. Rill opens Camellia’s hand and finds that it’s full of peppermints. Seeing this, Rill realizes Camellia was sexually assaulted by Mr. Riggs and tries to calm her sister down. During their next bath, Camellia screams and fights back. She is taken away and doesn’t return. Several days later, still reeling from the loss of Gabion and Camellia, Rill sees Lark being taken away by a couple. Rill tries to stop this, but Miss Dodd suppresses her. Rill tells Miss Dodd her story and Miss Dodd promises to help, but she’s caught by Murphy. Rill is locked in the basement and not allowed out, leaving Fern alone. When Rill is let back up, she finds out that Fern was adopted and slips into a deep depression. Several days later, however, the same couple who adopted Fern—Darren and Victoria Sevier—adopt Rill because Fern won’t stop crying for her. Reunited with Fern, Rill decides it’s time for them to run away and find their parents. They do this with the help of a young woman named Arney, who knows how to get to the Mississippi River. When Rill and Fern find their family’s shanty boat, the sisters learn that Queenie passed away and that Briny has become an alcoholic. One night, Briny drunkenly releases the boat into the river during a storm and the boat is destroyed by a floating tree. Rill decides she must bring Fern back to their adoptive family where they’ll be safe.
As Avery learns in the present day, Queenie’s twins were not stillborn, but were sold to different families. As adults, Rill and Fern were able to reconnect with Judy and Lark. Although they kept their relationship a secret, the women spent as much time as they could together in the house in Augusta. Avery decides to reunite Judy and May—the sole surviving Foss children—and tell her parents about the family secret. When Wells finds out, he is stunned but agrees that the sisters should be reunited. To that end, the Staffords arrange for May to move into the same facility as Judy, where the two sisters enjoy spending as much time together as possible. Avery is transformed by her the discovery of her family’s true history and decides to change her own life plans—she takes a job as a lawyer for a senior rights PAC and breaks up with Elliot in favor of starting a new relationship with Trent.
