Since 1948, when the Communist Party took over Czechoslovakia, the secret police persecuted priests who were unwilling to adapt to the new conditions. In order to control and manipulate the church, the state created Pacem in Terris, a collaborationist clerical organisation implanted into the ecclesiastical structures.

While some priests joined Pacem in Terris for the benefits offered by the organisation, others did so with the hopes of protecting the church’s mere existence, which was otherwise under constant threat.

In response, an underground church was formed with the goal of maintaining spiritual purity, ordaining secret priests and serving informal mass in private homes, all the while staying independent of state affairs.

The film takes place in the early 1980s. Three decades into Communist rule, Czechoslovak society is undergoing steep moral decline, but still no one dares to believe that the regime could one day come to an end.