Marius Vallois is 12 years old and needs a father. Marie Vallois has a 12-year-old son, heavy work responsibilities, a lover to calm, a position to fill, an adored sister and a complicated cousin, but no father for Marius. Robert Pique has a steam iron, is always late with the laundry, a Chinese fantasy, a neighbor who he protects and is looking for a job. Monsieur Papa is a story of a curious link which weaves between these 3 characters. A link which will give them difficulty and attachment for life.