 Charles befriended and was thought to be trying to influence the Dauphin, and was apparently involved in a botched coup d'état in December 1355 whose purpose appears to have been to replace John II with the Dauphin.John amended matters by making his son Duke of Normandy, but Charles of Navarre continued to advise the Dauphin how to govern that province.There were also continued rumours of his plots against the king, and on 5 April 1356 John II and a group of supporters burst unannounced into the Dauphin's castle at Rouen, arrested Charles of Navarre and imprisoned him.