Kate Parker is living a stressful life, and most of the stress is generated inside her own head. She's obsessed with statistics--two glasses of wine lower your risk of a heart attack, but three increase you chances of cancer, 85% of bicycle casualties involve riders not wearing helmets, etc. She governs her own life by the pursuit of the greatest possible safety, and does the same with her eleven-year-old son, Jack.
There's a reason for her anxiety, and her desperate attempts to keep her son and herself perfectly safe. On her wedding night, her parents died in a bizarre accident, killed when the taxi taking them home, driving on a dark road, hit a dead elk who had been shot by a poacher and then stumbled off to die in the road. Six years later, her beloved husband Hugo is killed by a gang of young toughs out to steal his expensive new sports car. It's all too much, and Kate is fighting fate to keep her son safe. To that end, she moved from London to Oxford, to be near her in-laws, so that they could help with Jack.
But her in-laws are increasingly worried by the effects of her paranoia on Jack. And when she starts finding small things missing, or says she does, and hearing strange noises, everyone knows it's Kate's anxiety kicking into overdrive.
Even Kate knows this.