New England, Summer, 1951-When a thirteen-year-old boy drowns in the Charles River, a family is left devastated, and the town of Norumbega is changed forever.

Eight years later, Frances Adams lives in the shadow of her dead brother Mac. She feels no identity, until she meets model Gwen, whose mystique inspires her to reinvent herself. When Gwen vanishes into the river and is presumed drowned, Frances becomes obsessed with her memory. She transforms herself into Gwen's likeness and feels a power she has not felt before.

An investigation begins, and the police question three men last seen with Gwen. Frances and her friend Iris follow them to the local riverside park, where one of the men-the suspicious Harris-mistakes Frances for Gwen. Intrigued by the idea of haunting him, she continues her secret pursuit, drawing him closer as she immerses herself in the case. As the mystery unravels, shocking revelations about its connection to a long-ago family tragedy surface.

In 1974, the former riverside park is excavated for new development, and two buried pasts are coming to light. Soon Frances will discover that the connections between Mac, Harris, and the mysterious Gwen are more profound-and chilling-than she ever imagined.