The Reading Group at the End of the World

One sunny day in May, Madeleine Grey, a girl with Swedish roots, arrives in the village of Ljusskär in Skåne, southern Sweden, as a new intern for the popular Free Church congregation. However, her stay ends abruptly when one evening she packs her suitcase and disappears without a trace. When, thirty years later, her sister Patricia receives an anonymous letter with Madeleine's necklace, she decides to travel to the small seaside village to make one last attempt to find her sister.
Patricia stays at the only local hotel, Monin's Bed, Breakfast & Books, where many of the locals go for a chat and Monin's famous homemade seaweed pastries. Patricia soon gets to know several women from the book club and, during conversations about literature, love, and marital disagreements, they try to get to the bottom of Madeleine's mysterious disappearance together. But not everyone is equally helpful, and Patricia learns that her questions are reopening old wounds.
What happened to Madeleine on that fateful late summer evening, and what is the dark secret that the people in the village guard so closely?