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.