At the height of the Industrial Revolution, a nun and a labor inspectress investigate linked cases in the silk industry.

The time: the Industrial Revolution. Claude is among the few women to pass the state exam and become a labor inspector, but she still dresses like a man when on the job. When young worker dies in an accident at a wire factory, Claude is the first to recognize him as the frozen body that turns up months later at an ice house. At the nearby Perrin silkworks, Sister Placide runs a boarding school. She is troubled by a new student who looks just like a former one from fifteen years ago. These two mysteries turn out to be connected, uniting Claude and Sister Placide in an investigation that brings them up against the taboos and prejudices of their time.