Sam is a charming, charismatic fifteen-year-old boy who makes friends easily and takes good care of his single mum, Jenny. Jenny is an insecure nurse who's addicted to prescription medication. She doesn't pick up on the little signs; the fact Sam doesn't yawn when others do; doesn't have an instinctive reaction when others display distress or joy - because Sam is a psychopath - a psychopath with murderous thoughts. And what Jenny doesn't realize is that his open access to the geriatric ward where she works is fueling his nascent compulsion.