A team of scientists clambers down into the steep crater of an active volcano in central Africa, a lake of molten lava seething far below. The team's mission is to explore this deadly mountain up close to find out when and why it is likely to erupt next. the lives of half a million people living directly in its shadow are at stake. In January 2002, the ground close to the city of Goma in the Democratic Republic of Congo split open and rivers of lava swept through entire neighborhoods, killing some 100 people and leaving 120,000 homeless. The volcano towering over the city, Mount Nyiragongo, had awoken again. Now French volcanologist Jacques Durieux and his team worry that, next time, deadly lava could erupt from cracks directly under the city itself.