It's the night of the full Cold Moon - the month of December according to the lunar calendar. A young man is found dead in lower Manhattan, the first in a series of victims of a ruthless killer calling himself the Watchmaker. His obsession with time drives the Watchmaker to plan the murders with the precision of fine timepieces, and the victims die prolonged deaths while an eerie clock ticks away their last minutes on earth. Amelia is not only Lincoln's eyes and ears at crime scenes on the Watchmaker case, but she's now running her own homicide investigation - her first case as lead detective. The policewoman's unwavering efforts in pursuing the killers of a businessman, who left behind a wife and son, sets into motion clockwork gears of its own, with consequences reaching to people and events that will endanger not only many lives but Lincoln's and Amelia's future together.