Willow Rather is a lonely Chicago transplant who decides to return to her small town of Heron Lake and to Aaron Rather, the grandfather she loves. While Willow is still wrapping up her affairs in Chicago, Aaron Rather dies in a fall that is officially deemed a suicide. Despite the existence of a suicide note, Willow is convinced that her grandfather was murdered, and she returns to Heron Lake to ferret out the truth.
Aaron's death and its aftermath cause a reluctant psychic to come forward, and soon everyone questioning the suicide is in danger. Stymied by the lack of a clear motive and hampered in the investigation by their own police department, Officers David Kennison and Doug Podgorski struggle to net a wily, determined adversary. As the threat to the town escalates, David must deal with mounting tensions in his marriage, and Doug begins to fear that his deepening feelings for Willow may never be reciprocated.
Despite a breakthrough in the case provided by an unexpected source, the two officers find themselves locked in a game of catch-up with a killer whose obsessive quest manages to put everybody to the test.