When a travelling salesman dies in a single car accident on a quiet country road, Chief Superintendent Lawson labels it a drink driving case. But when Constable Parks reveals the corpse’s face was blue, Dr Blake is intrigued. Although the victim’s clothes reek of alcohol, Blake concludes that the salesman was not drunk and certainly died before the crash. But how? And why is the face blue? Back at the scene of the accident, Danny is bitten by a snake while fossicking in the dead man’s car. During the autopsy, Dr Blake notices fang marks on the salesman’s leg and realises it’s a snake bite. He races out to the crash site where he finds Danny unconscious and rushes him to hospital. Dr Blake and Jean head to the boarding house where the dead salesman had been staying. Blake snoops around the boarding house and finds a locked basement. That night Blake returns to the boarding house and breaks into the basement and makes an alarming discovery that shocks everyone.