Note:  Do not rely on this information. It is very old.

Cinq Mars

Cinq-Mars, Henri, Marquis de (1620-1642), son of Marechal, the Marquis d'Effiat, and favourite of Louis XIII. He was introduced at court by Cardinal Richelieu, and his figure and manners soon made him a great favourite and secured his advancement, But his ambition outstripped his discretion, and looking on Richelieu as the great obstacle to the carrying out of his ideas he joined with the king's brother in a plot to murder the Cardinal. For his share in this conspiracy he was executed at Lyons. De Vigny has made his story the subject of a romance.