In the wake of their parent's separation, three siblings spend the summer in the south of France with their estranged Grandfather. In less than 24 hours, a clash of generations has occurred between the teenagers and the old man. During this turbulent summer, both generations will be transformed by one another.
Magali plays in a brass band. Guillaume drives a small tourist train. Both spin a perfect love, they share modest dreams and their baby is about to come. But an unexpected news upsets their routine: a man appears and announces that he is Guillaume's estranged father and also reveals that Guillaume is his legitimate heir of a kingdom offshore of France and England. Guillaume and Magali start to dream of a life as monarchs, surrounded by faithful subjects in their castle, enjoying their wealth. But reality is often different to what you can imagine.
Élise Lafontaine has a secret routine. Every morning and evening for many years, she has been waving at the express train that passes her house. One fateful day, she finds a letter from the train conductor in her garden and her lonely life is turned upside down. She engages in a promising correspondence through poetic and thoughtful letters where the two anonymous writers share their worlds with each other. But Elise’s fairytale is cut short when the train line permanently detours for a shorter route to Paris. Not willing to do without her daily delight, Elise prompts a daring escape from her comfort zone and sets out to find the train conductor.
