Which historical conspiracy is portrayed in Alfred de Vigny’s Cinq-Mars?

Alfred de Vigny’s 1826 historical novel, Cinq-Mars, portrays the conspiracy led by Henri Coiffier de Ruzé, marquis de Cinq-Mars, against the powerful first minister of France, Cardinal de Richelieu.1

Cinq-Mars, a favourite of King Louis XIII, sought to remove Richelieu from power to gain political influence. The plot involved high-ranking nobles, including the king’s brother, Gaston, Duke d’Orléans, and included plans to incite revolts and open French frontiers to the Spanish. In 1642, Cinq-Mars signed a secret treaty with King Philip IV of Spain to secure military aid for the rebellion. However, the conspiracy was exposed when a copy of the treaty fell into Richelieu’s hands, leading to the arrest, conviction, and execution of Cinq-Mars.234