Countess Charlotte and Baron Edouard, once madly in love, meet by chance twenty years after having last seen each other. They decide to marry and devote their time to their relationship and the development of their land. The couple are joined by Otton (an architect and Edouard's close friend) along with Charlotte's goddaughter, Ottilie. After a communal reading of a treatise on "elective affinities" - the inexplicable law that separates paired elements and makes them change partners - the two couples experience the same results. After a passionate night between Charlotte and Edouard a child is born that mysteriously ressembles Ottilie and Otton. The life and death of the child dramatically marks the parallel progression of the two love stories.