'If I had to choose, I'd rather have a sister over parents. I'd rather you over anyone.'
Mara and Nell will never be able to forget the day that their parents' marriage fell apart. They declare their family of origin wrecked, and the traditional structure to be a complete farce. From now on, all they have is each other. So in their twenties, they make a pact: no marriages, no babies and no repeating their parents' mistakes.

But a few years later, Mara does the unthinkable - she falls in love and becomes a mother, leaving Nell behind. Mara wishes that Nell could relate to her new life - its terrifying claustrophobia and unexpected joys - but Nell hardly recognizes her sister or the path she has chosen. Their pact now irrevocably broken, Nell throws herself into a relationship with a dreamboat of a man without asking whether they want the same things, or if she's willing to compromise her hard-won independence. A cosmic fork in the road has changed everything between the sisters, and just when they need her the most, they're confronted by the shadow of their mother's absence and the secrets they've all been keeping from each other.