If Balzac hadn't convinced me of le horreur of the French provinces Chabrol would have done so. Actually I can see Chabrol (if he were still around) wanting to film this story. It has all his favourite things- emotionally-crippled sophisticates and emotionally-crippled yokels circling one another in what turns out to be a dance of death. The landscape is beautiful and doesn't care. The mistral blows the leaves from the trees in early summer and withers up the silly English gardens the silly English attempt to cultivate in the rocky Cevennes. You want green lawns? stay in the Cotswolds.
The title very neatly embraces all the themes of the book. Firstly the silly English are trespassing in a landscape and a culture they don't understand and it hurts them. Secondly there are boundaries- drawn on the ground or understood to be there in family relationships- that we trespass across at our peril. Finally trespasses are those things we do to others and others do to us that we pray to be forgiven and to forgive because there's no other way to win free from the gravitational pull of the past.