Writer Philippe Claudel’s sensitive debut as a director does not seem dramatic, at least on the surface. However, it has such a good performance from Kristin Scott Thomas that you don’t mind a plot that turns on the kind of small detail that other movies would ignore.

Like the British Unrelated, reviewed here last week, it seldom puts a foot wrong and is pretty strict on avoiding melodrama.

Scott Thomas plays Juliette, a tired-looking fortysomething woman who has been in prison for 15 years for a crime that is not revealed at first, but that we gather is pretty terrible. We don’t know that when we first meet her waiting rather anxiously at an airport in France to be picked up by Léa, her sister (Elsa Zylberstein).

She is taken home where Léa, married with two adopted Vietnamese daughters, also looks after her husband’s ailing father (Jean-Claude Arnaud). Léa has a full life and doesn’t welcome her sister’s occasional stroppiness.

I’ve Loved You So Long is essentially about how Juliette’s crime affected both sisters and how they gradually begin to rebuild their once close emotional ties.

Claudel builds the drama out of everyday events — such as Juliette trying to find employment without giving away her secret, being taunted by a guest at a family dinner party or befriended by Léa’s colleague Michel (Laurent Grevill).

Scott Thomas, acting in French, is brilliant at suggesting a woman with a devastating past who still has a mordant sense of humour as well as a basinful of self-pity. The entire cast act with a naturalness that assists Claudel to show how Juliette’s visit affects everybody in varying ways. 

It’s a long film, but more engrossing than it first appears, since we hope Juliette and Léa will find a way to forgive and forget while at the same time wondering exactly why Juliette did what she did.

We find out in the end, and it is perhaps the least effective moment in the film. But before we do, Claudel proves that he understands his characters and sympathises with them equally. When the French do this kind of thing well, they do it very well indeed.