One or the Other (1974)

Stony broke college dropout Bernd Ziegenhals (Jürgen Prochnow) discovers that the dissertation by a renowned Berlin sociologist is a plagiary. The professor, Dr. Rüdiger Kolczyk (Klaus Schwarzkopf), initially gives in to Ziegenhals' blackmail and pays up, but he is out for revenge. When he tries to bluff his way out of more payments, Ziegenhals ups the ante. It turns personal. The psychological tug-of-war between the two escalates, with the threat level rising to include bodily harm, arson and attempted murder…