But as they stood there looking across, a horrible realization dawned on him. They had been so caught up in their desire to get to the river that they had not considered how they were going to cross it. Surely they couldn't swim – who could tell what dangers lurked beneath that still surface?

As though echoing his thoughts, Halima spoke. 'We need to find a boat.'

Ben looked left and right. There was no sign of anything. 'How are we supposed to do that?' he asked.

Halima shrugged. 'By looking.' She strode off along the river bank, with Ben following behind.

They spent the next half-hour searching along the bank for a boat. It was treacherous work, as they kept losing their footing on the mossy boulders, and all of a sudden the humidity had seemed to double in intensity. 'The rains,' Halima murmured at one point. 'We need to cross before they come.'

'Fat chance,' Ben said, knowing that he was sounding a bit surly. 'Look, Halima. Everyone lives on the other side of the river. Why would they leave a boat here-?'

He cut himself short as Halima looked at him triumphantly. There, a metre or so below the high bank on which they were standing, water lapping against its sides, was a small wooden boat. It was an insubstantial thing, rickety and unimpressive, but it was a boat nevertheless. Ben grinned as he felt relief surge through him.

It was short-lived. The instant his eyes fell on the boat, he heard a shout behind him. He spun round and, a sickness rising from his stomach, saw the sight he had been dreading: Suliman's men, twenty metres away, emerging from the forest, their guns pointing in his direction.

'The boat,' he yelled at Halima. 'Get in the boat! Now!'

His shout was punctuated by the sound of gunfire. Half expecting that he had been hit, Ben grabbed Halima and they jumped into the boat. It was barely big enough for the two of them, and as they hit the decks it wobbled precariously, water sluicing in and settling in the bottom of the hull. There was one oar there; Ben grabbed it and used it to push against the bank as hard as his strength would allow. The boat shot out a few metres into the river before slowing down to a gentle drift as the pair flattened their bodies into the bottom of the vessel, vainly attempting to hide from the onslaught of bullets as Suliman's men fired at them from the river bank.

But the sound of bullets never came. Instead, there was a short, muffled scream.

Gingerly, Ben looked over the side of the boat towards the bank. What he saw, he knew he would never forget as long as he lived.

One of the men – the smaller of the two – was already down, floored by an enormous silverback gorilla who had evidently attacked them from behind. Now the gorilla was dealing with the taller man. With one swoop of his enormous arm, he sent him crashing to the ground. The man weakly tried to get up and gain control of his gun, but he was too slow; the gorilla was beside him, raising both hands into the air, then thumping them down with brutal efficiency onto the man's chest. Again and again he beat him, roaring deeply each time he did so and inflicting the blows so hard that blood started to explode from the unconscious man's mouth and stick to the animal's long fur.

The gorilla continued his work long after it was clear to Ben that the man was quite dead.

When he had finished, the silverback turned his attention back to the smaller man, pummelling him repeatedly to make sure he would never get up again either. And then, without even seeming to acknowledge the presence of Ben and Halima, he turned and disappeared into the bush, growling deeply as he did so.

Maybe Ben was fooling himself, but he almost thought the animal seemed satisfied with his work.

Ben and Halima sat up in the boat in shocked silence; the rainforest itself seemed hushed after that horrific display. Ben watched in distaste as three vultures, silently swooping down as though surfing on an invisible tide of misfortune, settled on the bodies of the dead men and started pecking small, red gobbets of flesh from their faces. He turned away, sickened, and tried to focus on something else.

Halima was right. The river was not as wide here as it had been at their previous stopping point; but it was still wide enough – forty metres, Ben estimated. There was a gentle current that was pushing them downstream, but it was not so strong as to make using the oar too difficult, so he crouched in the middle of the boat and paddled alternately on either side, careful to keep his footing and gradually inching closer to the far bank. The boat still wobbled treacherously, and it was all he could do to keep his balance. Halima seemed able to do nothing but stare at the dead bodies on the bank. 'I told you terrible things would happen to them,' she murmured.

Ben didn't reply.

It was strangely peaceful in the middle of the river. Ominously peaceful. The oars splashed regularly as Ben eased them slowly towards the other shore.

Splash.

Splash.

Bang!

Suddenly he felt something knock the boat. He lost his balance and allowed himself to collapse heavily into the hull in an attempt to stop from falling sideways. 'What was that?' he demanded, sudden panic in his voice.

Halima shook her head to indicate that she didn't know; as she did so, they felt the boat being knocked again. More water sloshed over the side, stabilizing it a little but pushing the rim of the boat down a little too close to the water for comfort.

And then they saw what it was that was knocking them.

At first it looked like an enormous grey boulder was emerging from the water. It was Halima who realized what it was first. 'Hippo!' she gasped.

Instantly Ben grabbed the oar and, half kneeling, half standing, raised it up into the air to bring it sharply down on the head of the emerging beast. 'No!' Halima told him.

He looked questioningly at her as the hippo butted the boat once more, then allowed himself to sit down again as the vessel rocked dangerously.

'You cannot fight a hippo!' Halima told him scathingly. 'It is more dangerous than anything you have seen.'

'A hippo?' Ben asked, disbelievingly. But as if to back up what Halima had said, the boat was butted again, much more strongly this time. Ben and Halima grabbed firmly onto the side as it tipped almost to the point of capsizing – saved only by the fact that Ben had the presence of mind to hurl himself in the opposite direction and counterbalance his weight. 'What do we do?' They were both sopping wet and gasping for air, having swallowed large gulps of the river water.

'Hold tight and keep quiet,' Halima told him. 'Our only hope is that the hippo will leave us alone. If it thinks there is danger in the boat, it will continue to attack and that will be the end of us.'

Ben nodded, and the two of them lay down in the pool of water that had collected in the hull, their clammy bodies pressed together as they clutched tightly on to the edge of the boat.

The vessel swayed sickeningly, still reeling from the last knock. With every moment that passed, Ben expected to be hurtled down into the water. He knew he could probably swim to the other side if that happened, but he had no idea what horrors would try to stop him if he ended up in the water. And then there was Halima. 'Can you swim?' he asked her.

'Ssshhh!' Halima reprimanded him, before adding, quietly, 'No.'

Great, Ben thought to himself.

They continued bracing themselves for another knock.

But it didn't happen.

'I think it's gone,' Ben whispered. Slowly he pushed himself up, his hands splashing in the water that had collected in the hull. He looked around him. Everything was calm – there was no sign of hippos or anything else. As he looked around, the hippo emerged once more, but further away from the boat this time. It was heading towards the far shore, towards the place Ben and Halima wanted to get to. But there was no way they could follow; Ben saw that now. 'I'm going to let the current drift us downstream a bit,' he told Halima. She eyed the hippo as it waded out of the water on the other side and nodded her agreement.