When the death of a child in a hit-and-run shocks the quiet seaside town of Oyster Hill, police officer Luci Miller is called in to investigate. Her only clue is a fragment of car paint found at the scene—a unique shade of red that could help identify the killer.

Luci's investigation leads her to Jo Nelson, a grandmother in her seventies, who is deeply affected by the tragedy. She has watched too many parents suffer the loss of a child, having devoted decades of her life to keeping her son Oliver, born with cystic fibrosis, alive. Jo suddenly finds herself in the middle of the chaos when her family falls under suspicion.

The closer Luci gets to Jo, the more she struggles to maintain objectivity. Jo is charming and charismatic—but she has secrets and knows how to keep them. As the investigation draws in around her, Jo must confront the possibility that someone she loves has done the unforgivable.