She'd had an idea to call the novel 'Les Bessons' ('The Twins'), although she thought that although a great number of people would have understood the word, Parisians wouldn't have, (and presumably the more common 'Les Jumeaux' would have been unsatisfactory because it wouldn't have suggested the Berry vocabulary). Certainly much of the focus of the book is about the relationship between the identical twins Landry and Sylvinet Barbeau: only identical physically in the early stages but mentally as time goes on Landry is seen as more independent, outgoing and strong, whereas Sylvinet is mentally weaker, introverted, dependent on Landry and separation from him has such an effect that his mother fears for his sanity.
The split between the twins comes when Landry is chosen, at the age of fourteen, to leave the parental farm and live on a neighbouring one. This is torture to Sylvinet, who is jealous of Landry's new life, of the new friends he finds, in spite of Landry returning to the parents' farm on Sundays. Sylvinet is in such a state of turmoil that he runs from home and hides away, Landry goes to find him, but he's in none of their old haunts. And this is where the book takes a vital turn.
There's a nearby house where the old Fadet lives, and she's rumoured to be a witch, but she doesn't know where Sylvinet is. She lives with her grand-daughter Fanchon, or 'La Petite Fadette', who is disrespected because she's 'masculine', ugly, dirty, has dark skin and is said to have the witch gene. Her mother left her parents to run off with a soldier. She knows where Sylvinet is, but to find out Landry has to promise to grant her any wish she chooses: he has no choice, and uncannily his brother is exactly where she says.
It's some time before Fanchon reveals her wish: she wants Landry to dance only with her at the local dance, which means that he can't dance with the beautiful Madelon, who has the hots for him. And they are both insulted: Landry for inexplicably monopolising the local scarecrow witch, and Fanchon for what she is. She leaves Landry and tells him to dance with whoever he likes.
Landry follows her and finds her crying. And so begins a long, secret and innocent love story between Fanchon (who has something of the 'masculine' George Sand about her) and Landry. Fanchon though is no easy catch as she doesn't believe Landry is serious: he can't possibly want to marry her? That would be difficult as Landry's father thinks she's trash.
Fanchon decides to go to work in town for one or two years to repair her reputation, but returns after a year as her grandmother has died. Landry sees her in secret, and she's developed into a rather different person, and of course they still love each other. Meanwhile Sylvinet is wasting away, and Landry has been sent to another farm.
Fanchon secretly visits Barbeau as she can't understand what her grandmother has left her, makes him swear he'll not tell anyone, and it transpires that she's richer than him: grand-mother Fadet hardly spent anything but saved almost all her customers had paid her for over the decades. Barbeau makes sure Landry knew nothing about this, so loved Fanchon for what she is, and then visits the town to inquire about Fanchon's behaviour. He's not only pleased that Fanchon wasn't pregnant, but that everyone has very good words to say of her. Sounds like the marriage is on.
Which of course it is, but Sylvinet is getting worse, although the magic Fanchon soon cures him. In the end there's a double wedding joining the two farms, although Sylvinet goes off to become a successful officer.