Det Enda Rationella plot
Fifty-year-old Erland Fjellgren lives in an industrial town, works at the local paper mill and leads a seminar on marital problems at the local Pentecostal church with his wife. Everything runs smoothly until he meets Karin, the wife of his best friend Sven-Erik, at a party. The erotic tension between Erland and Karin is obvious and the situation becomes untenable. So Erland proposes a "rational solution": to face the crisis, it is enough to live together in the same house, in a kind of commune, with house rules and a division of work, and wait for this extramarital passion to disappear by itself. But that leads to dangerous situations…