Baron Brusenhielm at castle Tröstehult in Skåne dislikes how his young son Karl Oscar is playing “mother and father” with the tenant’s daughter Ann-Marie, as he anticipates the beginning of a future misalliance. Years pass, and Karl Oscar is about to graduate high school. He pretends to study church history but reads in fact “The Seducer’s Diary” and thinks of Ann-Marie, who is now grown up into a woman.