Un château en Espagne 25 years old

Like every year, Inès takes the train to Mont-de-Marsan to spend a week's holiday with her grandmother. But this time around, things do not happen as usual. First, Granny is late to the appointment outside the station. And when she finally arrives, she looks strange, seems to have difficulty in finding her way back home and mostly seems to be hiding something for her granddaughter...