The novel is set in the rustic fenland landscape west of Nantes, known as Brière, in which the traditional occupation of peat-cutting is becoming increasingly unsustainable as the peat runs out.
Aoustin, a rough peat-cutter and "ranger" employed to protect the traditional rights of the people of Brière, comes into conflict with his wife and daughter.
Having returned home to the ile de Fédrun after a long trip, he discovers that his wife, Nathalie, has sold the family linen to fund their estranged son who lives in Nantes.
His daughter Théotiste now also wants to marry a lad from outside the region, from a despised village of basket weavers, who are traditionally looked down upon by the independent-minded fenlanders.
Aoustin is given the task of finding a lost historical document signed by Louis XVI confirming the rights of the local people.
He travels throughout the fens to find whether any of the locals possess it, eventually locating it in the home of Florence, a madwoman who lives inside an ancient dolmen.