Christina Baker Kline’s 2026 novel, The Foursome, is a work of historical fiction inspired by the true story of the author’s own ancestors. Kline is known for best-selling novels such as Orphan Train (2013) and A Piece of the World (2017), which often center on the overlooked experiences of women in history. Told from the perspective of Sarah “Sallie” Yates, The Foursome follows Sallie and her ambitious younger sister, Addie, in 19th-century North Carolina. Their lives are irrevocably altered when they enter into an unprecedented marriage with the world-famous conjoined twins Chang and Eng Bunker. Set in the decades surrounding the US Civil War, the novel examines the social and moral landscape of the antebellum South. As the two couples navigate life in a shared household, Sallie must contend with intense public scrutiny, complex domestic tensions, and the deep moral questions of her time. Through their stories, the novel explores themes of Compromising Personal Morals for Power, The Constraints of Family Loyalty, and The Way Silence Preserves the Status Quo.

This guide refers to the 2026 first edition published by Mariner Books.

Content Warning: The source material and guide feature depictions of illness, death, child death, pregnancy loss, graphic violence, rape, sexual violence, physical abuse, emotional abuse, child abuse, racism, ableism, addiction, substance use, and sexual content.

Plot Summary

In the early 1840s in Wilkes County, North Carolina, unmarried sisters Sarah “Sallie” Yates and Adelaide “Addie” Yates live a circumscribed life on their family’s plantation, their marriage prospects dimmed by a past scandal involving Sallie. Their world is upended by the arrival of Chang and Eng Bunker, the world-famous conjoined twins from Siam, who have purchased land to build their own plantation. The sisters, particularly the beautiful and ambitious Addie, are fascinated. They finally meet the twins at a wedding, where the bold Chang immediately courts Addie, leaving his more reserved brother, Eng, to converse with the plainer Sallie.

The twins soon host a quilting party at their grand new home, making it clear that they’re seeking wives and proposing a secret courtship. Sallie is hesitant, but Addie, desperate for a more extraordinary life and leveraging Sallie’s past indiscretion, persuades her. Their secret meetings at an abandoned farm deepen the connection, as the twins recount their lives of being exhibited across the globe before gaining their independence. When Sallie and Addie’s father, David, discovers the affair, he forbids it, but a trip to Philadelphia, Pennsylvania, to stop the twins from undergoing a dangerous separation surgery solidifies the sisters’ commitment. After receiving a formal request from the brothers, David reluctantly grants his blessing.

Following a scandalous engagement and a tense confrontation with a local mob, the sisters proceed with a double wedding at their family home, Mulberry Farm. On the wedding night, Sallie is horrified as she witnesses Chang and Addie consummate their marriage in the shared bed. When her turn comes with Eng, she’s overcome with revulsion and flees to a separate room, creating a deep rift among the four. Chang angrily confronts Sallie, reminding her that leaving would ruin not only her own reputation but also Addie’s, as the law would invalidate her marriage.

Feeling trapped, Sallie finds a surprising connection with Eng through novels and games of chess, and their relationship slowly blossoms into a genuine, passionate love. Soon, both sisters are pregnant. They give birth to healthy, separate daughters—Sallie’s Katie and Addie’s Josie. However, life as a single foursome proves untenable. The constant tension between the sisters and the bickering between the brothers leads Sallie to write a letter to Eng, proposing that they divide into two households. The brothers agree, purchasing land in nearby Surry County and building a second house a mile from the first. Addie and her children move into the new house, while Sallie and her family remain in the original. The brothers establish a strict schedule, alternating between the two homes for three days at a time.

The new arrangement eases the daily friction, and the families settle into a rhythm. The farms, however, struggle financially, forcing Eng and Chang back into show business with P. T. Barnum. Their long absences strain the families, and the tours themselves are grueling and humiliating. Upon returning, Chang’s alcohol use and temper worsen, leading to escalating arguments with Eng. They investigate the possibility of getting surgically separated but are told that the operation would likely be fatal.

A deeper crisis strikes Sallie when she discovers peanut shells left by Eng outside the door of Grace, an enslaved woman who has worked for the family for years. Sallie realizes with horror that Eng has been forcing himself on Grace and is the father of her children. The confrontation shatters their marriage; though Sallie stays, she secures a promise from Eng that he will never touch Grace again, and an unbridgeable emotional chasm forms between them.

The outbreak of the Civil War brings new hardships. The twins, enslavers themselves, support the Confederacy, and their eldest sons, Christopher and Stephen, enlist. Sallie, influenced by her abolitionist aunt Joan and her own conscience, begins attending Quaker meetings, creating a deep ideological divide with Addie and the twins. The war brings shortages, fear, and deep loss. Sallie’s daughter Julia Ann dies of pneumonia at 19, and two years later, Addie’s daughter Josie dies of heart disease.

When the war ends and the enslaved people on their farms are freed, Grace leaves to find her mother. The families are plunged into financial ruin and physical hardship, forced to manage the farms themselves. Grace eventually returns, but on her own terms, negotiating a wage, a proper house with a lock, and the right for herself and her sons to learn to read.

The family’s financial desperation forces Eng and Chang back on the road. The tours are initially successful, allowing them to pay off their debts. However, their health is declining. While on tour in Europe, Chang suffers a debilitating stroke that leaves his right side paralyzed. His physical dependence and bitter resentment lead to constant, vicious conflict with Eng. The conflict culminates in a physical fight where Chang pulls a knife, prompting Eng to demand a surgical separation from their local physician, Dr. Hollingsworth. He refuses to operate but promises to do so to save one if the other dies.

In January 1874, a severely ill Chang insists on traveling from Addie’s house to Sallie’s to adhere to their rigid schedule. His condition deteriorates, and in the middle of the night, he dies from bronchitis. Eng, physically attached to his brother’s corpse, panics. A frantic message is sent for Dr. Hollingsworth to perform the promised separation, but he’s away. Three hours later, surrounded by his and Addie’s families, Eng dies. The subsequent autopsy of the brothers reveals that they shared one liver, and any attempt at separation during their lives would have been fatal. The brothers’ wills leave their respective properties to their wives, securing their futures. 

Years later, in 1886, an elderly Sallie reflects on her extraordinary life from the Surry County farm, which she now shares with Grace, Grace’s son Isaac, and Aunt Joan. Her relationship with Addie has settled into a quiet, respectful peace. She has made a life for herself on her own terms, finding a hard-won contentment in her family, her memories, and the simple beauty of the world around her.