The Piarist monk Ödön Lénárd was the Hungarian priest who was in jail for the longest time (for 18 and a half year) under the communist dictatorship. An important part of his collection is his correspondence with his brother, Ernő Lénárd. The copied letters reveal a great deal about the conditions in prisons in socialist Hungary, and they are important sources on church history too. These letters are testimony to Lénárd’s spiritual resistance against the dictatorship. They make clear that imprisonment did not break Ödön Lénárd, who, after his last release in 1977, continued his silent struggle against the communist dictatorship: he became a pastor and a spiritual leader of adult groups and a clandestine community of secret Cistercian nuns.