Sophie Hannah takes the comforting scenes of everyday life and imbues them with a frisson of fear. Why is a young woman so unnerved by the presence of a visitors book in her boyfriend's inner-city home? And whose spidery handwriting is it that fills the pages? Who is the strangely courteous boy lingering at a child's birthday party when all the others have left? And why does the presence of a perfectly ordinary woman in a post office queue leave another customer pallid and quaking with fear?