Harry nodded. ‘Lucky the lava didn’t burn down the door and fill this floor too.’

‘As you can see, the windows and doors are in the wall facing away from Nyiragongo. It’s not the first time. The bloody volcano spews lava on this town every ten or twenty years.’

Harry cocked an eyebrow. ‘And still people move back?’

Van Boorst shrugged. ‘Welcome to Africa. But the volcano is bloody useful. If you want to get rid of a troublesome corpse – which is a fairly normal problem in Goma – you can of course sink it in Lake Kivu. But it is still down there. Whereas if you use Nyiragongo… People often think that volcanoes have these red-hot, bubbling lava lakes at the bottom, but they do not. None of them. Apart from Nyiragongo. A thousand degrees centigrade. Drop something down there and, pouf, it is gone. It returns as a gas. It is the only chance anyone in Goma has to reach heaven.’ He broke into a hacking laugh. ‘I witnessed an overenthusiastic coltan-hunter drop a tribal chief ’s daughter on a chain into the crater up there once. The chief wouldn’t sign the papers giving the hunters the right to mine on their territory. Her hair caught fire at twenty metres above the lava. At ten metres above, the girl was burning like a candle. And five metres further down she was dripping. I am not exaggerating. Skin, flesh, it flowed off her bones… Is this what you were interested in?’ Van Boorst had opened a cupboard and taken out a metal ball. It was shiny, perforated with tiny apertures and smaller than a tennis ball. From a slightly larger opening there hung a wire loop. It was the same instrument Harry had seen at Herman Kluit’s house.

‘Does it work?’ Harry asked.

Van Boorst sighed. He stuck his little finger in the loop and pulled. There was a loud bang and the ball jumped in the Belgian’s hand. Harry stared. From the holes in the ball were protruding what looked like antennae.

‘May I?’ he asked, and put out his hand. Van Boorst passed him the ball and watched with great vigilance as Harry counted the antennae.

Harry nodded. ‘Twenty-four,’ he said.

‘Same as the number of apples made,’ said Van Boorst. ‘The number had some symbolic value for the engineer who designed and made it. It was the age of his sister when she took her own life.’

‘And how many of them have you got in your cupboard?’

‘Only eight. Including this piece de resistance in gold.’ He took out a ball which gleamed matt in the light from the electric bulb, then returned it to the cupboard. ‘But it is not for sale. You would have to kill me to get your paws on that one.’

‘So you’ve sold thirteen since Kluit bought his?’

‘And for ever increasing sums. It is a guaranteed investment, Monsieur Hole. Old instruments of torture have a loyal body of followers who are keen to pay, croyez-moi.’

‘I believe you,’ Harry said, trying to press down one of the antennae.

‘Spring-loaded,’ Van Boorst said. ‘Once the wire has been pulled, the victim will not be able to remove the apple from their mouth. Nor will anyone else for that matter. Do not take step two if you want to retract the circular ridges. Don’t pull the wire, please.’

‘Step two?’

‘Give it to me.’

Harry passed Van Boorst the ball. The Belgian carefully threaded a biro through the loop, held it horizontal and at the same height as the ball and then let go of the ball. As the wire became taut there was another bang. The Leopold’s apple jiggled fifteen centimetres below the biro and the sharp needles sticking out of each of the antennae glistened.

‘A faen,’ Harry swore in Norwegian.

The Belgian smiled. ‘The Mai Mai called the device “Blood of the Sun”. This sweet child has several names.’ He placed the apple on the table, put the biro in the opening where the wire came from, pushed hard, and the needles and antennae retracted with a bang, and the royal apple regained its smooth round shape.

‘Impressive,’ Harry said. ‘How much?’

‘Six thousand dollars,’ Van Boorst said. ‘Usually I add a bit each time, but you can have it for the same price I sold the last one.’

‘Why’s that?’ Harry asked, running his forefinger over the sleek metal.

‘Because you have come a long way,’ Van Boorst said, blowing cigarette smoke into the room. ‘And because I like your accent.’

‘Mm. And who was the last buyer?’

Van Boorst chuckled. ‘Just as no one will ever find out that you have been here, I will not tell you about my other customers. Does that not sound reassuring, monsieur…? See, I have already forgotten your name.’

Harry nodded. ‘Six hundred,’ he said.

‘I beg your pardon?’

‘Six hundred dollars.’

Van Boorst emitted the same brief chuckle. ‘Ridiculous. But the price you mention happens to be the price of a three-hour guided tour of the nature reserve where there are mountain gorillas. Would you prefer that, Monsieur Hole?’

‘You can keep the royal apple,’ Harry said, taking out a slim wad of twenty-dollar bills from his back pocket. ‘I’m offering you six hundred for information about who bought apples from you.’

He placed the wad on the table in front of Van Boorst. And on the top an ID card.

‘Norwegian police,’ Harry said. ‘At least two women have been killed by the product over which you have a monopoly.’

Van Boorst bent over the money and studied the ID card without touching either.

‘If that is the case I am truly sorry,’ he said, and it sounded as if his voice had become even more gravelly. ‘Believe me. But my personal security is probably worth more than six hundred dollars. If I were to talk openly about all the people who have shopped here my life expectancy would be…’

‘You should worry more about your life expectancy in a Congolese prison,’ Harry said.

Van Boorst laughed again. ‘Nice try, Hole. But the Chief of Police in Goma happens to be a personal acquaintance of mine, and anyway -’ he threw his arms in the air – ‘what have I done after all?’

‘What you have done is less interesting,’ Harry said, taking a photo out of his breast pocket. ‘The Norwegian state is one of the most important providers of aid to the Congo. If the Norwegian authorities ring Kinshasa, name you as a non-cooperative source of the murder weapon in a Norwegian double murder, what do you think will happen?’

Van Boorst was no longer smiling.

‘You won’t be falsely convicted of anything, gracious, no,’ Harry said. ‘You’ll just be on remand, which should not be confused with punishment. It’s the judicious confinement of a person while a case is being investigated and perhaps there are fears that evidence may have been tampered with. But it is prison nevertheless. And this investigation could take a long time. Have you ever seen the inside of a Congolese prison, Van Boorst? No, I suppose there are not many white men who have.’

Van Boorst pulled the dressing gown round him tighter. Eyed Harry while gnawing at the cigarette holder. ‘OK,’ he said, ‘a thousand dollars.’

‘Five hundred,’ Harry said.

‘Five? But you-’

‘Four,’ Harry said.

‘Done!’ Van Boorst shouted, raising his arms into the air. ‘What do you want to know?’

‘Everything,’ Harry said, leaning against the wall and producing a pack of cigarettes.

When, half an hour later, Harry stepped out of Van Boorst’s house and into Joe’s Land Rover, darkness had fallen.

‘The hotel,’ Harry said.

The hotel turned out to be right down by the lake. Joe warned Harry against swimming. Not because of the guinea parasite he would be unlikely to discover until one day a thin worm began to wriggle under his skin, but because of the methane gas that rose from the bottom in the form of large bubbles that could render him unconscious and precipitate drowning.

Harry sat on the balcony, looking down on two long-legged creatures walking stilt-like over the illuminated lawn. They looked like flamingos in peacock costume. On the floodlit tennis court two young black boys were playing with just two balls, both so ragged that they looked like rolled-up socks sailing to and fro across the semi-torn net. Every now and then aeroplanes thundered across the sky, above the hotel roof.