On 3 June 1991 at 3.18pm, a pyroclastic flow erupted from Mount Unzen in Japan. A cloud of superheated gases and particles descended at more than 100mph from the peak of the volcano, consuming everything in its path.It instantly killed Katia and Maurice Krafft, volcanologists and film-makers from the Alsace region in France. They were too close. They were almost always too close. On the day before they died, Maurice said in an interview, 'I am never afraid, because I've seen so many eruptions in 25 years that, even if I die tomorrow, I don't care.'The Fire Within pays homage to the Kraffts, who left an archive of more than 200 hours of footage of their final journey, unprecedented in its spectacular and hypnotic beauty.