In a web of lies, one mother fights for the truth.

For popular true crime author Margo Box, the past six months have been a waking nightmare. Ever since her five-year-old daughter, Poppy, vanished—abducted by her own father—Margo has tortured herself the way only a mother could: with unrelenting blame. How could she have let this happen? Had she been working too hard to see the signs?

Despite the guilt and unanswered questions, Margo holds on to the hope that Poppy is somehow still alive. Yet after years of solving other people's cold cases, her own case proves impenetrable.

That is, until she finds a cryptic letter hidden in a secondhand book in her neighborhood library box. In this letter are clues that someone in the community knows something about the disappearance of Margo's school friend Sarah nearly two decades ago—the disappearance that drove Margo into true crime and haunts her still. To distract from the pain in her life, Margo throws herself into Sarah's case, desperate for closure of some kind. But as she digs deeper into her friend's history, she unearths a disturbing connection to her daughter she never expected to find.