On a stifling summer's day, eleven-year-old Jack and his two sisters sit in their broken-down car, waiting for their mother to come back and rescue them. Jack's in charge, she said. I won't be long.

But she doesn't come back. She never comes back. And life as the children know it is changed for ever.

Three years later, mum-to-be Catherine wakes to find a knife beside her bed, and a note that says: I could have killed you.

Meanwhile Jack is still in charge - of his sisters, of supporting them all, of making sure nobody knows they're alone in the house, and - quite suddenly - of finding out the truth about what happened to his mother.