For many people the memory of February 16, 1983 ('Ash Wednesday') will take a long time to fade. For Caird Ramsay of the CSIRO Division of Building Research, the terrible destructiveness of that day has never been far from his thoughts, but for a scientific reason. Within a day of the disaster, he and his fellow fire researchers began a new and unexpected project: a detailed study of the fires and the effects they had on buildings. Why did one house burn while an apparently similar one, perhaps on an adjacent block, survive?