The subject of the present article is the activity of Rev. Prefect Szczepan Stanisław Soszyński in the light of the documents (decade reports) of the District Office of Public Security in Przasnysz, in the years 1945-1950. The documents mainly consist of extracts of his sermons as well as third party statements and the assessment of educational activity in schools. Przasnysz was Soszyński’s first pastoral assignment in the Diocese of Płock, where he acted as the prefect of lower and upper secondary schools. He won considerable respect of his pupils. He paid much attention to instilling Christian faith among young people. He was known for propagating the cult of St. Stanislaus Kostka among his pupils, for whom he was a role model, which was later proved by many of his pupils choosing the way of priestly vocation. He was a teacher in schools in Przasnysz until 1950, when he was expelled from school by state authorities for “educating young people in the spirit hostile to People’s Republic of Poland”.