'Deliciously ingenious.' Daily Mail 'Keeps you guessing right to the end.' PETER MAY 'Smartly entertaining.' Washington Post 'So beautifully written, so gripping, so perfect.' SOPHIE HANNAH If you're on the list you're marked for death. The envelope is unremarkable. There is no return address. It contains a single, folded, sheet of white paper. The envelope drops through the mail slot like any other piece of post. But for the nine complete strangers who receive it - each of them recognising ...