The first programme follows an extraordinary expedition to one of the world's most dangerous, spectacular and lesser-known volcanoes - Nyiragongo. The volcano contains a massive boiling cauldron of molten rock - the world's largest continually active lava lake. But it is also one of the most dangerous volcanoes on the planet. It has erupted twice in the last 50 years, most recently in 2002, wreaking havoc and destruction on the people who live in the nearby city of Goma. This region is also dangerous for another reason - it has been racked by war and humanitarian crises for most of the last 30 years, so Nyiragongo is one of the least studied active volcanoes on Earth. But now, an international and local team of scientists are mounting a major expedition to study the volcano. They are attempting to discover the warning signs that it is building towards a new eruption, so they can alert the people of Goma before it erupts again.