Girls of Brackenhill / Kate Moretti.

When Hannah Maloney's aunt dies in a car accident, she returns to her family's castle in the Catskills and the epicenter of a childhood trauma: her sister's unsolved disappearance. It's been seventeen years, and though desperate to start a new life with her fianc�e, Hannah is compelled to question the events of her last summer at Brackenhill. When a human bone is found near the estate, Hannah is convinced it belongs to her long-lost sister. She launches her own investigation into that magical summer that ended in a nightmare. As strange happenings plague the castle, Hannah uncovers disturbing details about the past and startling realizations about her own repressed childhood memories. Fueled by guilt over her sister's vanishing, Hannah becomes obsessed with discovering what happened all those years ago, but by the time Hannah realizes some mysteries are best left buried, it's too late to stop digging. Overwhelmed by what she has exposed, Hannah isn't sure her new life can survive her old ghosts.