 Presumably on the day before the eruption, David packs Linda and her son off to safety and stays behind for the scientific work he still needs to do on a ridge a few miles north of the volcano.Later that night, he pays a last visit to Harry.On the morning of May 18, 1980, David hikes to a ridge 6 miles (10 km) north of Mount St. Helens to monitor a massive bulge that has been growing on the north face of the mountain for the past few weeks, while Harry goes fishing in Spirit Lake at the foot of the mountain.