In the peaceful world of Little Nicholas, there is Daddy, Mommy, the school, but above all, his band of friends. They are called The Invincibles, but above all they are inseparable. At least they think so. But when Dad gets a promotion and announces that the family is moving to the south of France, Nicolas' world falls apart. How can he imagine life without his best friends?

During the German occupation of World War II, François, Eusèbe, and Lisa, three courageous children, embark on a secret adventure: resisting the Nazis in the heart of France. Through sabotage, hidden messages, and perilous escapes, they carry out clandestine actions right under the enemy's nose. Daring and friendship are their only weapons in the fight against injustice.