According to the lunar calendar, seasons are marked by each recurring full Moon. In December, The Full Cold Moon appears and nights are at their longest and darkest...A killer is on the loose in Manhattan. When a young man is found dead on the first of December on the Lower East Side, the victim of a prolonged death set to an eerie clock ticking away his last minutes on earth, Lincoln Rhyme and Amelia Sachs coin the murderer the Watchmaker. The killer's obsession with time drives him to plan murders with the precision of fine timepieces, and it's up to Lincoln, Amelia, Lon Sellitto, Ron Pulaski and the rest of the crew to stop the Watchmaker from carrying out his future plans. But while Amelia acts as Lincoln's eyes and ears at crime scenes on the Watchmaker case, she's now running her own homicide investigation--her first case as lead detective. Her unwavering efforts to find the killers of a businessman who left behind a wife and son set into motion clockwork gears of their own.As the two cases race along almost in real time, the twists and surprises come fast and furious. The Watchmaker may not be simply a murderous lunatic, but a far more cunning villain than anyone could guess. And Amelia's case has unexpected consequences that may endanger many lives, and even Lincoln's and Amelia's future together.