After a grisly murder in a shabby New York bookstore, Detective Callum Doyle starts receiving sinister phone calls. Doyle is told more deaths are planned but the caller will give him clues, on the condition that he keeps them to himself. As more vicious deaths follow, the pressure on Doyle to find a link becomes unbearable. Does he continue to gamble with people’s lives? Or should he sacrifice everything to defeat a ruthless and manipulative enemy?