A Strange Love (1984)

After a hot and steamy company party, Sibylle and Harald, both in their late thirties, spend the night together. They meet each other later and resolve to enter into a strictly intellectual relationship. He is a widower with two sons, with the younger son just entering school. She is single and relatively satisfied in her relationship with a married colleague. Suddenly, Sibylle quits her job at the company's staff canteen and delves into her new self-appointed task with fiery fervor: to pep up Harald's family life, turning his house, garden, etc. inside out. Harald, a quiet man used to peace and his own habits, starts to flee from her on a daily basis. Without love, she figures, the relationship will not work out. But it does not take long for the pair to miss each other's presence.