What did the Gnostic box hide, discovered on the eve of the Great French Revolution on the territory of the once-existing Templar commandery in Essarois in Burgundy; what secret united the dignitaries of the Order of the Temple, who, during the arrest, were kept in the Coudre donjon of the Chinon castle and left their mysterious graffiti on the donjon wall in 1308; how the templars came to be associated with the Mandaeans, followers of John the Baptist (Yochanan Ha-Matvil). All this and much more is covered in the investigation of military historian Vladimir Tkachenko-Hildebrandt and the works of three French-language authors of the 19th century - Prosper Mignard, Joseph von Hammer-Purgstall and Jules Loiseleur, translated into Russian for the first time. The book is the first part of an anthology dedicated to mysticism and the religious-mystical movements of the Middle Ages and the Renaissance, one way or another associated with the Order of the Poor Knights of Christ and the Temple of Solomon and its legacy.