The Distant Hours by Kate Morton

It starts with a letter, lost for half a century and unexpectedly delivered to Edie’s mother on a Sunday afternoon. The letter leads Edie to Milderhurst Castle, where the eccentric Blythe spinsters live and where, she discovers, her mother was billeted during World War II. The elder Blythe sisters are twins and have spent most of their lives caring for their younger sister, who hasn’t been the same since her fiancé jilted her in 1941. 

Inside the decaying castle, Edie searches for her mother’s past but soon learns there are other secrets hidden in its walls. The truth of what happened in “the distant hours” has been waiting a long time for someone to find it. In this enthralling romantic thriller, Morton pays homage to the classics of gothic fiction, spinning a rich and intricate web of mystery, suspense, and lost love.