There was a horrible silence, then the man who had been forced to kill his friend spoke. 'But boss, how are we going to get them? They have taken the only vehicle left in the village.'

Suliman smiled a dead smile. 'No they haven't,' he said. 'Come with me.'

He turned and started jogging back into the village, his men following nervously behind.

They were perhaps seven or eight miles out of the village – Ben couldn't tell for sure as he had been concentrating so hard on just keeping the Land Rover on the road – when they came to a halt. The forest on either side of the road was very dense – it would be impossible to drive any vehicle off the road and round any obstruction – and this particular stretch of road was long and straight; from where they had stopped, they would be able to see people coming – in either direction.

'This'll do,' Ben said, pointing just ahead of them and to the side of the road. If they could block the road just here, there would be no way anyone could reach Udok by car and it would be a long walk with the dangers of the jungle either side; if Ben could get his message through to Sam Garner again, perhaps they would have gained the time they needed to seal the village before anyone else could get in and be infected. And, of course, no one could now leave by this road and take the virus out of Udok either. He hoped.

The two of them opened their doors simultaneously and climbed down. Halima was clearly in great pain, but she said nothing about it. Wordlessly Ben took the axe from the back of the truck and headed to the side of the road.

He had his eye on a tall tree – tall enough, he estimated, to cover the width of the road once he had felled it. It was not as thick as some of the trees around, but it was thick enough – if he was going to hack it down, it would take some work. Ben raised the axe over his right shoulder and brought it down with all his force onto the side of the trunk that was furthest away from the road. The blade stuck into the bark and he had to give it a mighty yank to pull it back out again. The second swipe entered the tree several centimetres higher than the first cut. Ben's brow furrowed – this was going to be more difficult than he had imagined.

Meanwhile Halima was in the road, keeping watch. Their plan was to cut down the tree to stop any busload of workers being able to gain passage to the village; and they needed to have as much advance warning as possible if Suliman and his men were following. They didn't think there was another vehicle still in the village for them to use; but they weren't sure.

Ben kept hacking away. The sun was high and hot, casting short shadows on the ground; before long, sweat was dripping down his face into his eyes, and the handle of the axe was slipping in his perspiring palms. He felt his muscles burning with the exertion, and it was all he could do to keep going. But he gritted his teeth and thought of his father, bleeding and weak on that bed. If he didn't stop this busload of people from arriving in Udok, they would meet the same fate.

He was a third of the way through the trunk now. He continued cutting the tree, the occasional grunt of exertion the only sound punctuating the silence between him and the ever-observant Halima.

Suddenly she shouted, 'There is someone coming!'

Ben stopped, automatically looking back towards the village to see if Suliman was upon them. But there was nothing coming from that direction. With a sick feeling he turned round. Sure enough, indistinct because of the heat haze but definitely there nonetheless, he could see a minibus. It was impossible to say how far away it was, or how quickly it was travelling, but Ben didn't allow himself the time to stop and watch it, instead running back to the tree and redoubling his efforts with the axe.

'Hurry, Ben!' he heard Halima shout, panic in her voice. 'They are nearly here!'

Ben slammed the axe into the tree with as much force as he could muster; when he tried to pull it out, though, it would not come, no matter how much he tweaked and jiggled it. 'Come here, Halima!' he yelled.

She limped to his side, her black face strangely pale. 'What do you want me to do?'

'Push!'

There was no way, Ben realized, that he was going to cut all the way through the tree trunk before the minibus had passed them; their only hope was to pray that he had cut deeply enough into the trunk to be able to push it over and let the weight of the tree itself do the rest of the work. They placed their hands against the bark and started to take the strain.

There was a slight groan from the tree, but it only wavered fractionally. 'Again,' Ben shouted. 'One, two, three, push!'

Halima cried out a little as she put all her force behind it. This time there was more movement, and the sound of cracking from inside the wound Ben had inflicted on the trunk with his axe.

But now he could also hear the sound of the minibus, the rattly growl of its diesel engine growing nearer and nearer. They pushed again, and again. The trunk creaked and cracked, then finally – with a massive tearing noise – it toppled and fell over, landing with a heavy thump across the road. Ben heard the sudden squeak of brakes, and the two of them ran back into the middle of the road. The minibus had stopped about fifteen metres beyond where the tree had fallen, and the driver was climbing down, waving his arms at the two of them and shouting abuse in Kikongo. Then he was pushed to one side as two burly men jumped out. They took one look at Ben and Halima and started bounding towards them.

'Get in the Land Rover,' Ben shrieked. 'We can't let them get near to us, we might infect them.' But Halima was already halfway there. He clambered in and fumbled for the keys in the ignition. The men were jumping over the tree trunk by the time the engine coughed into action. He slammed the gear stick into reverse and moved backwards as quickly as he could. Yet again the engine started screaming as he hit top speed for the low reverse gear, and the men were gaining on him. Ben needed to speed up, but to do that he had to be facing in the opposite direction.

'Hold on,' he told Halima. 'I'm going to turn.'

Halima nodded and clutched the sides of her seat firmly. Ben took a deep breath and spun the wheel round quickly to the right. The tyres skidded noisily as the vehicle moved round through a hundred and eighty degrees before coming to a jolting stop. Ben knocked it into first gear again, then breathlessly moved away. In his wing mirrors he noted, with satisfaction, that his pursuers had stopped and were arguing angrily with each other as the Land Rover sped back towards the village.

They drove in silence as the road started curving round and the scene of chaos they had caused behind them disappeared from view. But they couldn't stay silent for ever. 'What are we going to do now?' Halima asked.

'I don't know for sure,' Ben replied. 'I think we should try and get back to Suliman's office, see if we can make that phone call again. All we've done here is buy ourselves some time but-'

He stopped in mid-sentence and slammed his foot on the brakes. Because there, in front of them, parked sideways across the road, was a car. The same car Ben, Charles and Abele had taken from the bandit the day they had arrived in Udok. Surrounding it were a group of armed men – Ben was too shocked to count how many – and at their head was the unmistakable tall, lanky figure of Suliman.

Ben's eyes narrowed as the man stared at him, a nasty sneer on his face.

Time seemed to stand still.

'Listen carefully,' Ben breathed, trying to stop his lips from moving. 'I think there's enough space for me to get round the side of the car. I'm going to drive straight at it until the last minute, then turn. As soon as we start moving, duck down out of sight, because they'll probably start firing. OK?'