Frederica Brahms is an artist who lost her husband to cancer two years ago. She knows she can't magically overcome her grief by moving. But she decides to relocate anyway, to the family home she inherited on the isle of Pendille in Saint-Joachim, a commune of eight islands in the center of the Brière marsh in France. She wants to make a new life for herself and to work on her genealogy too. There is a lot of her family history that consists of contradictory stories that she wants to clarify. While researching her house and her ancestors, she manages to clarify those stories and find the truth behind them. But while she now has answers to most of her questions, she has also uncovered a decades-old mystery surrounding one of her ancestors. It's a mystery that she desperately wants to solve. And almost everyone, including the chief of police, is happy to help her.