The French sociologist Gabriel Tarde is well-known for his theory of social imitation. His work Fragments d’une histoire future is less quoted as it is a prospective essay on the future of humanity. The article deals with the narrative of this history and focuses on the special writing of the end of a cycle. How do human beings react in extreme circumstances when one major source of energy disappears ? How do they change their traditional world vision ? What are the main values that we can save in order to ensure the revival of humanity ?