The following version of this book was used to create this study guide: Wingate, Lisa. Before We Were Yours. Wingate Media LLC, 2017.

Before We Were Yours begins in Memphis in 1939. Twelve-year-old Rill Foss lives on a shantyboat on the Mississippi River with her four younger siblings and her parents, Queenie and Briny. One night, Queenie, who is pregnant with twins, goes into labor, but she is having complications. Briny brings Queenie to the hospital and leaves Rill in charge. Shortly after, a group of policemen climb aboard the shantyboat and forcefully take Rill and her siblings. The children are brought to an orphanage run by three cruel women, Miss Tann, Mrs. Murphy, and Mrs. Pulnik. Soon, Rill learns that the name of the place is the Tennessee Children's Home Society (TCHS). At first, the children think that they will shortly be brought back to Briny and Queenie, but before long, they realize that they may never see their parents again.

At the TCHS, each of the children face abuse, neglect, and malnourishment. Her sister, Camellia, Rill's sister closest in age to her, is raped by one of the workers named Mr. Riggs. Shortly afterwards, she disappears, and Miss Tann tells Rill that she had never existed in the first place. Grieving the loss of her sister, Rill has no choice but to watch as each of her younger siblings are adopted by wealthy families and separated from her.

Rill and her sister, Fern, are adopted together by a wealthy composer and his wife. Mr. and Mrs. Sevier treat Rill and Fern well, and are grateful to have kids around the house after Mrs. Sevier lost several babies in childbirth. They call Rill and Fern "May" and "Beth," the names that Miss Tann gave them back at the TCHS. One day, Miss Tann comes back to the Seviers' house warning them that they could lose the children if they do not pay her more money. Rill decides to run away with Fern and travel on the river back to the Arcadia. When they finally arrive, Rill's friend Silas tells her that Queenie recently passed away, and Briny is now an alcoholic. A few days later, the Arcadia burns down and Briny is not found. Silas agrees to take back Rill and Fern to the Seviers, where they spend the rest of their childhood.

Meanwhile, in present day Aiken, South Carolina, Avery Stafford is a successful lawyer and the daughter of a senator. She has a handsome fiancé, Elliot, and lives a life of privilege. One day, when she visits the local nursing home with her father for a political event, a resident steals her bracelet. When the nursing staff later notify Avery and she returns to retrieve it, she meets with the elderly woman, whose name is May. Avery begins to visit May as she learns that she might have some connection to her Grandma Judy, who now has dementia.

Avery, eager to uncover the mysterious connection between May and her grandmother, searches through Grandma Judy's old daybooks and finds a phone number for someone on Edisto Island. Avery calls the number and learns that a man named Trent Turner had some confidential documents for Grandma Judy. Avery decides to travel to Edisto Island to retrieve those documents. There, she meets Trent Turner's grandson who goes by the same name. Trent is reluctant to help Avery at first, but eventually shows her the birth certificate and adoption papers for a child named Shad Foss from the 1939. Trent and Avery gradually develop a romance as Avery realizes that Elliot is not right for her.

With the help of Trent and May, Avery soon learns that her Grandma Judy and May are sisters. Judy is one of the twins who was born to Queenie in the beginning of the novel, and Shad is her twin brother, who she was apparently searching for later in life. The novel ends as May and Grandma reunite.