Rosso, a writer lacking inspiration, is invited to a book signing in a small village but it's a fiasco. As usual, he drinks too much and ends the night by destroying the moped of the man they call the Indian. Forced to go and apologize, he is surprised by a group of children, and together, they discover the Indian's corpse. The children know more than they let on, and manage to convince him to help them investigate the murder of their friend. He is then confronted with the world of children, a world made of stories, where reality is told and where things only exist because we believe in them. Little by little he has fun and finds his inspiration, but one detail escapes him, the children's desire for revenge. Rosso is suspected by the people of the village and the investigation turns into an expedition to prove his innocence. But the group is trapped by the real assassins, Jean and Saskia, the Indian's own sister. She wants to recover her inheritance, a treasure that the Indian secretly entrusted to the children. Rosso is sequestered and reveals the position of the fort. While he manages to escape, the children kill Jean who is chasing them. Everyone meets at the fort and war breaks out. Despite their tenacity, they cannot match Saskia's rifle, and Rosso sacrifices himself to allow them to escape. He and Saskia kill each other. Before dying, he left his book to them but it is up to them to write the ending.