Oda Bråthen loses her job as a copywriter in the advertising industry, and is contacted by a former client who wants to give her an assignment: To write a biography of Lina Fjeldbrinken, multi-millionaire and founder of the natural cosmetics brand "Linné AS". Oda accepts the assignment and travels to Koster, the Swedish archipelago where the old lady lives, to write the book. But the assignment will prove more difficult than Oda first thought, as the old lady mixes the story of herself as a young sickly girl at the sanatorium at Ekenäs and a as botanist who developed the cosmetic products at Koster, with outrageous tall tales and macabre stories. What is true and what is not? And what is a truth? Does something have to be credible to be true?

The entire time, the Koster archipelago (Sydkoster in particular) exists as a frame around them. At first glance, Koster offers the perfect Swedish summer idyll, but as the holidaymakers return home as the season ends, the restaurants close, a different version of the islands emerge. We learn more about both history of the islands and Lina Fjeldbrinken, and in creeps an unpleasant underworld of pig births, human experiments, female sex hormones extracted from urine and jealous husbands.