Every victim is found with a stopped pocket watch—and a nineteenth-century brass gear etched with a sealed court docket number.
When retired Superior Court Judge Arthur Sterling is found dead in his Beacon Hill study at midnight, FBI Behavioral Analyst Elena Vance and veteran Boston Homicide Detective Marcus Cole are called to a crime scene engineered like the inside of a Swiss chronometer. Resting on the judge's tongue is a brass escapement gear bearing the number of a sealed 2014 arson trial—the exact case Cole's former partner was investigating the night he was killed in a staged hit-and-run.
Asthe methodical killer known as "The Horologist" hunts down the five officials who buried the truth twelve years ago, the trail leads Elena and Cole from the subterranean archives of Boston to a snow-covered clockwork museum and antiquarian bookshop in Camden Harbor, Maine—and finally to a lethal conspiracy reaching the highest levels of the Justice Department. With the clock ticking toward the twelfth hour, Vance and Cole must decipher the secret of the brass gears before the real architects silence them forever.