Simone and Elliott Evans have it all; a comfortable life, a house on a quiet street, and two sweet daughters. But their marriage is far from happy, especially now. While Elliott spends all day at work, postpartum depression presses down hard on Simone’s shoulders. Baby Lizzy is colicky and often sick. Four-year-old Aster is a handful—not at all as good a “helper” as Simone had hoped. The more time Simone spends home alone with the girls, the more she’s convinced that Elliott’s interest in his family is waning. He’s pining for his ex, Leighton Prescott—a woman who mysteriously disappeared from their small New Hampshire town years before, leaving her and Elliott’s then newborn daughter, Aster, behind.

When Simone confronts Elliott in search of the truth, he reminds her that this isn’t the first time she’s accused him of being unfaithful, and it isn’t the first time her assumption has been wrong. But when Simone spots Leighton at the grocery store in their tiny hometown, she has her proof. Leighton Prescott is back, and despite what Elliott says, Simone knows Leighton will stop at nothing to destroy the life she’s built with Elliott, piece by precious piece.

Terrified of losing her family, Simone puts Elliott to the ultimate test. He’s left with one last chance to save the marriage he vowed to preserve. But rather than rekindling the love he and Simone once shared, he instead uncovers an unfathomable truth about the woman he calls his wife, a woman that, as it turns out, he doesn’t know at all.