Hanging in – or on – was a Herculean task that day. The track was a snake writhing through the scrub, grass and patchy forest. It went on forever. Occasionally we’d come upon other travellers, all of them baffling in their own way. Here was a man pushing a wheelbarrow full of painted sticks. Hours later, two children alone, neither of them more than three years old. The next person we saw was an old lady arguing with a donkey. It didn’t apparently want to take another step. We came to another, smaller river at one point. This one was crossed by a bridge. Quite a broad bridge, in fact, designed to take proper traffic. Marcel paused mid-span for a water break. I shut my eyes and tilted my flask to the sky; the sun broke through the clouds and warmed my face.

‘Who would bother to build a big bridge like this when the track either side of it is barely wide enough for a motorbike?’ I said.

‘The Belgians,’ said Amelia. Seeing that I was none the wiser she went on. ‘They were big into infrastructure. Sixty years ago this little track was probably a decent dirt road. Since the Belgians pulled out and the trucks stopped running, the surrounding bush has been trying to reclaim it.’

Mother Nature had done a pretty good job of that. In places the track was no more than a wheel’s width, and occasionally it disappeared altogether. But finally it wound back into the village where we’d first picked up the bikes. I was exhausted, dead on my feet, barely had the energy to climb into Marcel’s truck. When I shut my eyes all I could see was the bike’s front wheel rolling ahead of me, and the constant juddering through the handlebars ran through my whole body long after I’d got off the bike. Marcel seemed unaffected. He put a piece of chewing gum in his mouth and fired up the pickup. I’m ashamed to say I fell straight to sleep. Amelia did too. I felt bad not keeping Marcel company for the last leg of the journey, but I couldn’t help it. The next thing I knew we’d arrived at the airport.

We said our goodbyes to Marcel. I’m not sure I could have found the words to thank him properly in English, let alone French, but I wanted to try, and I made a right mess of it by asking Amelia to say that we were grateful to him for doing way more than we’d paid him to do. She translated his response. ‘This was never about the money. He hopes you find your parents. And he believes in what we’re trying to do. It’s what Innocent would have wanted. Get the evidence out there, he says. Do whatever it takes.’

I offered Marcel my hand. He took it, his palm cool. ‘Bonne chance,’ he said.