We were walking down the wide main street of Bunia, choked by the dust thrown up by passing four-wheel drive vehicles, some of them brand new. The street used to be surfaced but when it became more potholes than Tarmac they let it revert to dust. At one end stands a ghastly concrete tower with a sculpted hand clutching a flaming torch. It is the symbol of Zaire. It is disintegrating.
'In Europe you would not put up with what is happening here but that is our problem,' said Alphonse. 'We Africans are too passive. We accept the situation.'
I agreed but I wondered what the mystery was. To me it seemed brutally simple. There is no government any more. The armed forces stationed here are the only functioning representatives of the state, but in practice they are unpaid mercenaries from other parts of the country quartered on the city. Their official monthly pay - if it arrives - does not even buy a loaf of bread. So they exact tribute from the local traders. If the city merchants do not pay them regularly, they loot their shops.
This is not another poor corner of a poor continent. Bunia is more like a Wild West boom town. It is the centre of a gold-mining area and farmers here can get three harvests a year from the land. It grows good coffee and Bunia is a centre for trade stretching to Kinshasa, more than 1,600km (1,000 miles) to the west, and across Uganda and Kenya to the Indian Ocean in the east. The trade continues and the new cars are evidence that someone is doing well out of it, but Bunia is what happens when a state is destroyed.
In the VIP bar I bought Alphonse a beer and we sat listening to Phil Collins on a new sound-system. The bar was hung with modern paintings and monkey skins, and had old-fashioned fruit-machines. The bar stocked everything. Propping up the bar were four drunk whites who turned out to be the crew of a plane that had just flown in from the capital. They said it was carrying seven tons of money to buy gold from the local traders, who buy it from the freelance miners. Local people said it belonged to President Mobutu Sese Seko and was a regular visitor.
At the other end of town Dr Maurice Lendunga is struggling against an epidemic of bubonic plague. A small clinic next to his house has a constant stream of visitors. He and Alphonse, his assistant, are each paid 185 New Zaires a month. On Saturday that was worth dollars 2 ( pounds 1.35). On Sunday the New Zaire fell to 120 to dollars 1. By the time you read this their monthly salaries will probably be worth less than a dollar. The beer cost two months' salary.
They survive partly by selling some of the medicines given by Medecins Sans Frontieres which the organisation accepts as inevitable - even obvious. They each have five children to support. But their wives are the chief earners now and support their husbands and the children. Dr Lendunga's wife has built a bar next to their house and Alphonse's wife is a market trader.
These two highly qualified, competent and dedicated men, are now holding back a disease that could kill millions if it spreads. They are unpaid and unsupported, sustained only by their wives. Meanwhile, the country's leader, one of the world's richest men, prints money to send to Bunia to suck out the local wealth to add to his private horde.
I would call it madness rather than mystery.