Stefan Schröder is a trainee teacher for Latin and German. He has just moved into an apartment in an old, desolate house in the Berlin suburbs when he receives a letter from the school authorities: they have doubts about his loyalty to the constitution! From now on, Stefan feels persecuted, constantly watched and monitored in his apartment. Added to this is the fact that the actual, mysterious main tenant is away for an unforeseeable period of time and keeps one room locked. The suspicion that someone is going in and out of his apartment and that the people surrounding him are not who they claim to be becomes ever stronger. Stefan frantically searches for a motive.