In New Zealand the main trunk railway line and two state highways cross the foothills of three active volcanoes. On Christmas eve 1953, the crater lake on the largest of these volcanoes burst its banks sending a lahar down the mountain and into the path of a passenger express train carrying 285 people to their families for Christmas.

A government board of inquiry concluded the accident was an act of god. This documentary demonstrates that it was both predictable and preventable – an accident which should never have happened.