When she was sixteen, Diana left her unhappy family and set out to make a new life. Twenty-five years later, she has arrived. Recently married to Edmund, there are just the two of them living at Wynhope, his family's historic country home, both happy for the past to be locked away and for the future to be free from responsibility.

But when Diana hears that her mother has died, she impulsively asks estranged half-sister Valerie and her nine-year-old son to stay. The night of the funeral, fueled by wine and years of resentment, the sisters argue and a terrible accident occurs. The foundations of a well-ordered life start to crack and the lies begin to surface, one secret after another demanding a voice. And then there's the boy, watching, waiting.

The Half Sister is a profound and haunting portrayal of those who are imprisoned by the past and by their struggle to find the words which will release them.