It's late at night, and we're driving through the darkness of the Western Sahara in a rattly old Mercedes towards the border of Mauritania when I smell gas.
"Are you making tea down there?" I ask Amady. He's riding shotgun, and I notice he's fiddling with a propane burner on the floor in front of his seat. "That's crazy."
"I think it's strange, too," Amady says. "But the driver asked me to do it." He balances a small tray on his lap, pouring tea from one cup to another and then back into the pot to cool it off.
I met Amady, a young Senegalese musician, earlier in the day at a sun-baked, fly-infested rest stop on the second day of a 26-hour bus ride from Marrakech to Dakhla, the furthest point south reachable by Moroccan buses. In Africa, I soon learn, it's typical to spend 48 hours or more on the road: Amady is returning home to Dakar after a visit to Morocco that lasted just four days - less time than it takes to get there and back.
We pass the tea around the car. I've had tea in the Sahara before, but never quite like this.
I've noticed something about our driver: he's rather imperious for a man who drives a jalopy for hire. Perhaps it's an impression created by the neatly trimmed moustache and his gold-framed glasses, or the regal desert dress of his native Mauritania - a dishdasha with sweeping sleeves, armholes big enough to step through and a wide swath of gold brocade around the neck. But he's got the look of a man not accustomed to people telling him what to do. A man who makes his passengers serve him tea.
It's a long, straight road through the Western Saharan wastelands, and I start to worry that the driver might doze off. He stops the car repeatedly to stretch. Finally, we pull into a petrol station. He walks into an empty room and, without much explanation, falls asleep on a dirty mattress.
Come again? I knew we'd be spending the night on this side of the border, but I wasn't expecting this. There are no spare mattresses for Amady and me.
I'm too livid to sleep, even though it's my second consecutive night without a bed. I prop myself against the wall in the corner and weigh my options. I could kick the driver, but that wouldn't help; he does, after all, need the rest more than I do, for the sake of us all.
I start to calm down. Next thing I know, I'm asleep on the dirty carpet, a condition that persists for a few precious hours.
We queue at the border before dawn and cross into Mauritania at nine, going off road for several kilometres into an undulating no-man's-land riddled with mines and wrecked vehicles - travellers who didn't manage to follow the tyre tracks of previous cars' have been blown to smithereens in recent years. It's a landscape that's been compared, correctly, to Mad Max.
Time was when Mauritania was not, in fact, the end of the world. It would be nice to tell the grandchildren I saw Chinguetti, for instance, the country's main tourist draw, about 500 kilometres inland. The Sahara is slowly swallowing the former caravan hub, once a beacon for poets and scholars. But I've decided to go straight through to Dakar, and I see little of Mauritania except a desolate coast.
Amid a chorus of shouting in Hassaniya (Mauritania's language, an Arabic dialect indecipherable to most Arabic speakers), Wolof (the language of Senegal) and French (the lingua franca), we change cars in dusty Nouakchott, the capital, and reach Rosso, the border town, after dark.
We bribe our way through the border, which is officially closed, paying off a gang of Wolof-speaking miscreants who hang around outside the immigration office. I thought I'd be in good hands with a local, but the ordeal nearly brings Amady to tears.
Beneath an inky sky, a barely buoyant skiff brings us across the Senegal River, a geo-cultural divide. There's music coming out of the speakers in the town on the other side of the river, with not an Arab note to be heard; nor is sweetened tea served at all hours. We're out of the desert now and into black Africa.
But the journey's far from over. I spend a third consecutive night without a bed when the car gets a flat about 4am. We stop outside a tyre shop on the side of road and wait for dawn amid the high-pitched screech of mosquitoes.
I reach Dakar at 10am, 66 hours after leaving Marrakech, and find a guest house facing the Atlantic. The ocean is restless, endlessly crashing against the fine sands, but for the first time in days, I sleep soundly. In a bed.
Scott MacMillan is blogging about his journey on his website, www.wanderingsavage.com