Even before the royal family returned to Paris, it was discovered that von Fersen was one of the people who facilitated their escape, and a warrant was put out for his arrest. Von Fersen left France and in Koblenz he put himself in touch with Comte d'Artois, the exiled prince, and Charles Alexandre de Calonne, the former Controller-General; together they made plans to convince the other European powers to declare war on France. In Brussels, von Fersen worked out a steganography technique for writing with Beaumont and Marie-Antoinette: