The Hidden CityIt's 1879, and Lenox is convalescing from the violent events of his last investigation. But a desperate letter from an old servant forces him to pick up the trail of a cold case: the murder of an apothecary seven years before, whose only clue is an odd emblem carved into the doorway of the building where the man was killed. When Lenox finds a similar mark at the site of another murder, he begins to piece together a hidden pattern which leads him into