The Safekeep by Yael van der Wouden

It is fifteen years after the Second World War, and Isabel has built herself a solitary life of discipline and strict routine in her late mother's country home, with not a fork or a word out of place. But all is upended when her brother Louis delivers his graceless new girlfriend, Eva, at Isabel's doorstep - as a guest, there to stay for the season…

In the sweltering heat of summer, Isabel's desperate need for control reaches boiling point. What happens between the two women leads to a revelation which threatens to unravel all she has ever known.