The Summer of Katya by Trevanian
In the golden summer of 1914, Jean-Marc Montjean, recently graduated from medical school, comes to the small French village of Salies to assist the village physician. His first assignment is to treat the brother of a beautiful woman named Katya Treville. As he and her family become friendly, he realizes they are haunted by an old, dark secret . . . but he can’t help falling deeply in love with Katya.
Jean-Marc is warned by Katya’s brother that she is delicate and that he should curb his attentions, but he is young, hopeful, and in love . . . and he is certain that Katya returns his affections. When Jean-Marc learns that the Trevilles are planning to leave the village forever, he insists on a final meeting with Katya. That meeting and the events that follow turn what was an idyllic romance into an unending nightmare. Katya’s secret is revealed in a thrilling tale that is part love story and part psychological thriller, and the chilling climax will stay with the reader long after the last page is turned.