This paper examines the eighteenth-century Kostroma Christ-believers’ community. It is based on the 1747 police investigation case against the merchant Ivan Krupennikov, held in the Fund of the Most Holy Synod at the Russian State Historical Archive. One of the important figures in the case was Anna Stepanova, a peasant from the Kostroma district, revered as the Theotokos. The paper introduces new archival materials and describes some religious practices of heterodox communities in eighteenth-century town of Kostroma.