Marius Vallois is twelve years old and needs a father. Marie Vallois has a twelve-year-old son, major professional responsabilities, a lover to calm down, a post to fill, an adorable sister, a complicated cousin, but no father for Marius. Robert Pique has a steam-pressing business, piles of garments to dry-clean, a Chinese fantasy, a female neighbor who he protects and he's looking for work. Monsieur Papa is the story of a curious bond that will develop between these three characters, a bond that will make life difficult but that will connect them for the rest of their lives.