Eleven-year-old Dawn can always find hope - in a friendly pigeon, the patch of blue she sees out of the hole in her turret  roof and kindly Mrs Goring. But Tamara, the young woman, who says she’s Dawn’s mum, is visited by the scary Austen and he has plans for Dawn. When Mrs Goring disappears and a mistake with Dawn's ‘medicine’, causes her to notice things she shouldn’t, she pieces together clues about, Austen, Tamara, her real mum, and not so much who as what she is. 
Dawn is a stolen, 'spare' child (bred from 'spare' embryos to boost supplies of blood and organs for transplant). If she is not returned to the new building where all the spare children must be gathered before opening day, Austen and Tamara will be taken for 'spares' instead. Can Dawn escape, find Mrs Goring, her real mum, and prevent The Bonille Corporation, who run the 'spare' programme from sentencing hundreds of children born to be spare parts to a short anaesthetised existence and certain death?