The story of Lucien Deslinieres presents a historiographical interest in the study of both socialism and the first French Communists. As a republican journalist who became a socialist, a non-conformist Guesdist, and a frenzied anti-Marxist after a short but intense conversion to the Bolshevik cause, his fights led him from the Allier departement to Ukraine, from the Seine departement to the Eastern Pyrenees. Both a theorist and a publicist, he produced an abundant and sometimes disconcerting work that clearly included him in the lineage of utopian socialists. The recent opening of several fonds, in France and in the Netherlands, sheds light on his chaotic and poorly known career. His career before 1914 was representative of the rallying of many Republicans converted to socialism in the late 19th century. On the eve of Wold War I, he had become a recognized publicist within working-class circles. He was more a reformist than a revolutionary, and Jean Jaures prefaced his main work, L'Application du systeme collectiviste. The inability of Lucien Deslinieres to move up the governing bodies of the SFIO (the French Section of the Workers' International), the painful loss of his two sons during World War I, and the marvel of the "bright glimmer from the East", modified his path and thus explains his historical depth. Attracted to the Russian Revolution, Lucien Deslinieres, at the age of 60, headed to Moscow, where he had direct access to Lenin. His role in the process leading to the split of the Tours Congress had not been decisive, but he was among the few French militants who attended the first Comintern Congress during the summer of 1920. He was appointed People's Commissar in Ukraine and then in Turkestan, but was unable to implement his theories on land collectivization. He came back to France and broke away from the communist circles, but he could not find much support within the SFIO. Lucien Deslinieres returned to theory and started to write a monumental and anti-Marxist work, Le Socialisme reconstructeur, that had a sceptical and contemptuous reception: the utopians had become outmoded among the left wing groups between the two world wars. The famous publicist of the early 20th century died as an isolated and impoverished prophet.