People have been disappearing in what the explorer Stanley called the black heart of Africa - the impenetrable forests of northern Congo. But when a brilliant young English doctor vanishes, alarm bells really start to ring. Intelligence chief Jack Milton sends a message to his godson Luca Matthews (''The Forbidden Temple'' hero) in the Himalayas asking him to go to Africa and find Joshua. Reluctantly Luca obeys, but he is no longer the man he once was, traumatised by his part in the death of his best friend, his legendary climbing nerve shot to pieces. Meanwhile in Africa, mining troubleshooter and brilliant flying pilot, Beatrice (Bear) Makuru, also wants to brave the northern wilderness. Coltan is the mineral without which no mobile phone or computer would work. Explosions have been wrecking coltan mines. Bear needs to find out why. Her journey with Luca to Africa's black heart is the beginning of an utterly terrifying sequence of events, uncovering a secret so simple yet so startling that it could rock the foundations of the civilised world.