Accused of treason and stripped of his knighthood, Crispin Guest has survived on gritty streets of London by reinventing himself as The Tracker, an investigator for hire who can locate lost objects and uncover secrets. When the merchant Nicholas Walcote hires Guest to investigate his young wife Philippa for adultery, he discovers an underground world of danger and dirty dealings. Philippa is indeed hiding something-but she's not the only one. Walcote himself is rumored to possess a holy relic so powerful that some would even kill for it. To get to the truth about the mysterious Walcotes, Guest must contend with his nemesis, Sheriff Simon Wynchcombe, as be becomes entangled in a strange world of superstition, seduction, and murder.