The House at Winterkeep. Tide House Mysteries, #1

A death on the moors. An estate built on lies. When twenty-two-year-old Rowan Sherrard is found dead on the Yorkshire moor, it looks like a tragic accident. It isn't. She had been staying at Winterkeep - officially a conservation foundation, unofficially a place wrapped in silence and secrets. As Detective Inspector Honor Whitling investigates, she uncovers connections between Rowan's death, a long-sealed east wing, and a decades-old mystery of missing girls from an elite boarding school.
Then an old key surfaces - hidden for thirty-six years. Winterkeep is more than an estate. It is a carefully built system of lies, powerful enough to bury the truth for generations. For readers of Ann Cleeves, Kate Morton, and Elly Griffiths.