Eventually Suliman spoke again, and the vehicle came to a halt. Still pointing the gun at Ben, he opened the door and climbed out. 'Get out,' he said flatly.

Ben and Halima did as they were told.

'Go round to the front of the car, face it and kneel down.'

By now the two other men were in the road. One of them had his Kalashnikov trained on them, so Suliman let the handgun fall and threw it onto the passenger seat. As Ben and Halima knelt down in front of the Land Rover, Ben could feel the scorching heat of the engine against his face. It gave him no warmth, though; his whole body had gone cold with fear. He knew what these men had in their minds.

One of them said something in Kikongo, and the others laughed. 'He wants to know which one of you will be first,' Suliman called out.

More laughter.

'Gentlemen first, I think,' Suliman continued. 'That is the British way, is it not?'

Ben's body shuddered. The man with the gun was behind him – he could tell by the scuffing of his feet in the dusty earth. But how far? A metre? Five metres? He had no way of telling. 'I'm sorry,' he whispered to Halima. Her breath was shaking and tearful. Ben glanced to the side to see a look of terror such as he had never seen before.

'Do it,' Suliman barked.

Ben clenched his eyes shut, every muscle in his body tensing.

Click.

He started, the shock of the sound forcing his body forward.

Click.

The sound again.

Ben and Halima looked sharply at each other, both realizing what it meant. The rifle had stuck: they had one chance to get away. 'Run!' he shouted hoarsely. The two of them stood up, spun round and barged their way past the man, who was looking at his weapon in confusion. Ben caught another whiff of alcohol – clearly the guy was too bleary to have cocked the gun properly. They sprinted down the road, and as they did so, Ben heard Suliman screaming behind them in Kikongo. 'We need to get into the trees,' Ben panted at Halima, loud enough for her to hear but not so loud that the others would know what they were planning. 'After three, bear to the left, OK?'

'OK.'

'One.'

Bang! A gun fired, and just ahead of them Ben saw an explosion of dust where the bullet fell.

'Two.'

He heard the three men behind them arguing and shouting.

'Three.'

Immediately they veered right, plunging under the canopy of the rainforest. It was unforgiving and barely penetrable, but they had no option other than to fight their way through. Back on the road, they heard Suliman furiously shouting something.

'What's he saying?' Ben asked urgently.

For a moment Halima didn't reply, too intent on fighting her way through the verdant bush. But eventually she spoke.

'Track them down,' she translated. 'And kill them.'

A couple of years ago, Ben's mum had taken him to Kew Gardens in London. A typical Bel Kelland day out, with lots of lectures about the environment and what we were doing to it. What he remembered most, though, was the Palm House, a huge glass pavilion in which the heat and humidity levels were high enough for all the exotic trees and plants that were kept there. It had been oppressive after only ten minutes; but it was as nothing to the surroundings in which he found himself now. His face was moist, not only from the perspiration of running, but also from the thick humidity in the air – ten times worse now he was under the canopy of the rainforest than it had been in the village. His unsuitable Western clothes were already ripped by the angry thorns of the unfamiliar plants all around him, their tough, juicy leaves barbed on the edge like the teeth of a saw. Remarkably he had not yet cut his skin, but he suspected it was only a matter of time.

Halima led the way, deftly finding paths through the thick foliage that Ben would never have seen. Behind them they heard the shouting of the men, seemingly coming from different directions but in fact, Ben soon realized, confirming the fact that he was wildly disorientated. He had no idea if he was running north, south, east or west. All he knew was that he had to keep going. They ran blindly for at least half an hour, both of them breathless and Ben feeling a sharp stitch in the side of his abdomen; he forced himself to push through the pain barrier, however, knowing that the alternative was a lot less palatable.

Eventually they stopped, spent a minute catching their breath and then, barely daring to move, listened around them. It was not silent. The screams of unseen birds filled the air; closer to the ground were the shuffles and movement of unknown creatures. But the sounds they were listening for – the shouts of their pursuers and the noise of humans inexpertly cutting their way through the forest – were absent. Ben looked at Halima in relief; her eyes were flashing darkly and she returned his gaze with a coldness Ben hadn't expected. 'You OK?' he whispered.

'No,' Halima replied sternly. 'This is all your fault.'

Ben blinked at her. 'What do you mean?'

'Those men, they would have never done this to me if you had not interfered.'

'What are you talking about, Halima? They were going to kill both of us.'

'You pointed a gun at them!' Halima started to raise her voice, only lowering it when she saw Ben wince. 'Do you not understand what that means in these parts? There are bandits everywhere – if you threaten to kill someone, they will try to kill you first.' Her Congolese accent could not hide her fury. 'Those men were taking me to the village elders. I was to be punished for showing you the ritual last night. Not killed.'

'No, Halima.' Ben spoke firmly, urgently. 'You're wrong. Listen to me carefully. Your village is not cursed.' She tried to interrupt, but Ben spoke over her. 'Let me speak. You heard me tell Suliman that my father has become ill – I have as much interest in this as anyone. He's a scientist – a good one – and he thinks that there is some sort of virus down the mine, highly contagious. The people who run the mine know this, but they stand to make a lot of money from the Coltan down there. Suliman knows we're on to them. I wouldn't mind betting that he has orders to kill anyone who discovers the truth. That's why he was abducting you – he thought I had told you what was going on.'

Halima looked confused.

'Think about it, Halima,' he urged. 'Why would the village elders send three men with AK-47s to catch a fourteen-year-old girl? It doesn't make sense.'

'No,' Halima said. 'You don't make sense. If Suliman thought that there was a virus down there, why would he risk staying?'

'Because some people are immune. Like you, for example.' Halima's hand went up to the amulet round her neck, and she fiddled with it as Ben continued to speak. 'That's why they put Suliman and his men – people who they would never think of putting in positions of authority – in charge.'

For a moment Halima didn't reply, but eventually her wide eyes stared directly into Ben's. 'And what about you, Ben Tracey?' she asked in a low voice. 'Are you immune from this virus?'

'I don't know,' Ben admitted. 'All I know is this: if this thing spreads beyond your village, millions of people all over Africa could die. We have to alert the authorities, and we have to stop anybody from getting in or out until it's under control. We have to get back to Udok, Halima.'

Halima looked at him thoughtfully. 'You would really go back, even though you believe what you believe?'

Ben closed his eyes momentarily. The image of his father, lying helplessly on his makeshift bed, appeared in front of him. 'I haven't got any choice,' he whispered, before looking back at Halima. 'You don't believe me, do you?'

Halima shrugged slightly. 'I believe something in the mine has been disturbed. You call it a virus, I call it something else. If your plan is to close the mine down, then we both want the same thing.' Her voice softened slightly. 'And I am sorry about your father. I understand what you are feeling. I will help you.'