The weight of water - Anita Shreve

On Smuttynose Island, off the coast of New Hampshire, more than a century ago, two Norwegian immigrant women were brutally murdered. A third woman survived by hiding in a cave until dawn. In 1995, Jean, a photographer, is sent on an assignment to shoot a photo essay about the legendary crime. Taking her extended family with her, Jean stays in a sailboat anchored off the coast, and finds herself gradually becoming more and more engrossed in the bay's mysterious and gruesome past. Wandering into a library one day, she unearths letters written by Maren, the sole survivor of the murder spree. Jean's fear of losing all that she cares about is reflected in Maren's poignant tale of love and loss, and her obsession with the ancient story drives her to wild impulsive action -- with unrecoverable consequences.