„Un peuple et son roi" crosses the destinies of the men and women of the population, and those of historical figures. Their meeting place is the newly founded National Assembly. At the heart of the story lie the fate of the king and the birth of the French Republic.

Mathilde, aged 9, enjoys her last day of summer holidays at the seaside with her group of friends. Her father falsely interprets one of their games.

Tired of war, they set off on an adventure. The 20th century begins and the children play in the garden until the end of summer. Accompanied by his cousin Louis, his younger brother Ernest, and Marthe, the mischievous little girl, Paul will travel all the way to the Amazon to discover the mystery of Venus.