Five women became fast friends at university. Twenty years later they wonder if the people who know you best are the ones you can confide in.

The five of them - Stella, Priss, Kay, Helena and Polly - met at university, their lives full of lazy afternoons and late nights. Friendship seemed simple and there was such pleasure in the endless talk and in just living alongside each other.

Now the women are turning forty and they're finding that a shared past can sometimes be a burden. They're all struggling to navigate the ways in which their lives have differed from the plans they made themselves and the hopes they had for each other. In the past, solidarity came easily, but now they compare lovers, husbands, jobs, children and sofas, asking how the choices they've made or failed to make hold up.

As marriages end and secrets emerge, they wonder whether these people, the ones who know so much about them, are really the ones they can confide in.