Saltwater by Katy Hays

In 1992 Sarah Lingate is found dead below the cliffs of Capri, leaving behind her three-year-old daughter, Helen. Despite suspicions that the old-money Lingates are involved, Sarah’s death is ruled an accident, and every year the family returns to prove it’s true. But on the thirtieth anniversary of Sarah’s death, the Lingates arrive at the villa to find a surprise waiting for them—the necklace Sarah was wearing the night she died.