This movie connects with a previous Zanussi work, Illumination (1973). In the latter the protagonist is engaged in an unending quest for illumination, defined as "a revelation of truth beyond the senses." He looks for the ultimate truth along several paths; science, religion, relations with other people. In the end he does not succeed but the quest itself leads him to partial truths along the way.
In this much darker film the protagonist Augustin is a math professor in a German university. He is not engaged in the search for universal truth but rather in the understanding of concepts such as free will and the existence of God. He tests these ideas in slightly mad ways; to assert his free will he performs totally unmotivated, unnecessary actions such as: he climbs down a pipe, half naked, from his bedroom window to the icy street below in the dead of winter. His idea (mercifully not implemented) of testing if God cares about his existence is to play Russian roulette. His relations with other people are almost nonexistent; he firmly rejects psychoanalysis communicates via tape recorder but not personally with an old professor, his teacher, and is directed by him to an Orthodox priest with whom it has a long conversation (and immediately betrays by vandalizing his church).
He teaches Statistics at the university. His classroom is dimly lit, his students few and visibly bored. The board is full of formulas but we never see him writing one. He rambles about philosophy of mathematics such as: are sets a natural or artificial construct? Is mathematics invented or discovered? He lets one of his students devise and put in practice a way to win in roulette based on the false premise that a spin of the wheel depends on the result of previous spins (Incidentally no casino in the world would let anyone play roulette with a stack of computer paper full with numbers in front of him).
He is finally interned in a rather run down mental institution. There he commits an act of self mutilation. At this point the movie switches from murky black-and-white to color and one hopes that this announces some sort of solution or at least a mitigation of Augustin's problems. Nothing like this; the last scene shows that his condition has not changed. The final impression of the movie is that of the examination of a diseased mind that looks for some kind of truth but infallibly takes the wrong path at each fork in the road. It leaves a bitter taste in your mouth.
