A missing baby. A fraught friendship. A secret that can never be told. On a brisk fall night in a New York apartment, 35-year-old Billie West hears terrified screams. It's her lifelong best friend Cassie Barnwell, one floor above, and she's just realized her infant daughter has gone missing. Billie is shaken as she looks down into her own arms to see the baby, remembering—with a jolt of fear—that she is responsible for the kidnapping that has instantly shattered Cassie’s world. So begins the story of Billie and Cassie's friendship—both in recent weeks, and since they met twenty-three years ago, in their small Hudson Valley hometown the summer before seventh grade. Once fiercely bonded by their secrets, including a traumatic, unspeakable incident in high school, Cassie and Billie have drifted apart in adulthood, no longer the inseparable pair they used to be. Cassie is married to a wealthy man, has recently become a mother, and is building a following as a fashion and lifestyle influencer. She is desperate to leave her past behind—including Billie, who is single and childless, and no longer fits into her world. Hurt and rejected by Cassie’s new priorities, Billie will do anything to restore their friendship, even as she hides the truth about what really happened the night the baby was taken. Told in alternating perspectives in Lovering’s signature suspenseful style, Bye Baby confronts the myriad ways friendships change and evolve over time, the lingering echoes of childhood trauma, and the impact of women’s choices on their lifelong relationships.