Tess Gerritsen again weaves frighteningly realistic medical detail into heart-stopping suspense, as a small-town doctor races to unravel the roots of a violent epidemic - before it destroys everything she loves.

Lapped by the gentle waters of Locust Lake, the small resort town of Tranquility, Maine, seems like the perfect spot for Dr. Claire Elliot to shelter her adolescent son, Noah, from the distractions of the big city, and the lingering memory of his father's death. She's also hopeful that she can earn the trust of the town as she builds a new practice. But all her plans unravel with the news of a shocking incident: a teenage boy under her care has committed an appalling act of violence.

Claire has stopped prescribing a controversial drug to the troubled boy, a decision that some in town now second-guess. But before she can defend herself, a rash of new teenage violence erupts in Tranquility, forcing Claire to perform increasingly risky emergency procedures. And when one of her patients dies, the town's panic turns to fury.

Shaken by accusations, and fearful that Noah is now at risk, Claire desperately searches for a medical cause behind the murderous epidemic. She begins to suspect that the placid waters of Locust lake conceal a disturbing history - and an insidiously lethal danger. But while Claire races to save the town - and her son - from harm, she discovers an even greater threat: a shocking conspiracy to manipulate nature, and turn innocents to slaughter.