[3] The film is based on a 1970s screenplay written by Jean Gruault for François Truffaut, which in turn is based on the true story of aristocratic siblings Marguerite and Julien de Ravalet who were executed in the 17th century on charges of incest and adultery.

After Julien saves Marguerite from a horse riding incident, their uncle, Abbot, feels uneasiness in the siblings’ relationship.

He advises their father, Jean, to send Julien and his older brother, Phillipe, to study abroad on the excuse Marguerite is distracting their education.

The marriage quickly becomes extremely unhappy and Lefevbre begins physically abusing Marguerite.

Julien later finds out what is happening and frees Marguerite by beating Lefevre and allowing her to return home.

Their father contemplates sending Julien away but their mother, wanting to make her children happy, arranges for them to secretly run away together.

Lefevbre files charges against Julien and Marguerite for incest and adultery, and they are declared fugitives.

At trial, both deny the charges and claim they ran away because Julien helped Marguerite escape from her abusive husband.

[8] Boyd van Hoeij of The Hollywood Reporter called it "ambitiously mounted but wildly uneven".