Two sailors, Lasse and Karl Gustav, float ashore after a shipwreck. Visiting a castle a baron ask them to help him lay his hands on an inheritance by Karl Gustav posing as the heir of the castle.

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.