Ruth Furnival is a successful television executive with a seemingly perfect life: a nice house in London, a lawyer husband and two grown-up daughters. But at 54, with an empty nest and the menopause behind her, she feels restless and dissatisfied.

After multiple rounds of failed IVF, her eldest daughter Lauren has been told that the only chance for her and her husband to have their own child is surrogacy. So when Ruth discovers that, with the right dose of hormones, she could carry their baby, out of desperation they agree.

At first Ruth is buoyed up by her sense of purpose, but as the pregnancy progresses, long-buried events from her past resurface - and Lauren can't contain her corrosive envy. Isolated and alone, Ruth starts to unravel, and what started as an act of altruism begins to seem like an atonement for which she is willing to risk everything.