THE PARCHED HEART OF THE PDC is the three-day, 350-mile off-road desert crossing through the Parc National du Banc d'Arduin, in the south of Mauritania. There are no gas stations, freshwater sources, or route markers, so it's necessary to hire a guide and carry your supplies. Cars spin into sandpits, and radiators and gas tanks are bashed to pieces. Midday temperatures average 90 degrees.

With such potential for peril, I ditched Sid and Martin in Dakhla, the southernmost town in Western Sahara, after Ros Bif blew yet another head gasket.

The parched heart of the PDC is the 350-mile desert crossing. There are no gas stations, freshwater, or route markers. Cars spin into sandpits, and radiators are bashed.

If she punked out again in the sands, it would be almost impossible for the other teams to absorb three extra bodies and our gear. "So you're abandoning us," Sid said icily. "I see. When the going gets tough, you quit." He was looking for an excuse to launch a tirade, but I refused to light his fuse.

I set off the next afternoon in Team SloMoShun's VW Polo with Emma Barber, a tall blond businesswoman in her mid-thirties. Also on her team were her father, John, a stout 70-year-old mechanic with his wrist in a cast, and his wife, Fuzzy, a spunky 60-year-old with erect silver hair, both crammed into the Citröen. Emma's half brother, Joe, and his friend David, both in their thirties, rounded out the caravan in their eight-cylinder Rover 800. SloMoShun had earned a bevy of nicknames, including Team Panic, for their hysteria-inducing screwups, including leaving Fuzzy behind at a Spanish toilet stop for the better part of an hour. I'd dubbed them Team Posh for their habit of staying in luxury hotels and because they'd brought along a dozen or so bottles of red wine.

Our guide, Hamid, led us into what felt like a random stretch of Sahara in his white Toyota pickup, cajoling us with constant hand signals to step on the gas to avoid sinking. We blazed across the flats at 50 miles per hour until, 20 minutes in, Emma's Polo snagged in a drift. Everyone unloaded to dig us out, jamming carpet scraps under the tires for traction. "Oh, make sure to take some pictures!" Emma squealed.

At least a dozen rescues later, we stopped to camp. It took Team Posh an hour to put up one of four spanking-new four-man tents; in the meantime, I erected the other three and cooked dinner. "Oh, you're just what I thought an American would be like!" said Fuzzy. "So self-reliant!"

But the bonhomie didn't last long. The next morning, Emma's Polo stalled in an especially soft stretch of sand and we decided to leave the car behind. "Goodbye, little Polo," a grief-stricken Emma told her companion as we squeezed into the cab of Hamid's truck. Throughout the afternoon, we stopped time and again to morosely dig the other cars out. At one point, there was a wave of panic when John's hip went out of socket as he tried to peer under the Citröen. "Get in your truck and pull these cars out!" Fuzzy demanded of Hamid. "We're not paying you so this old man has to dig!"

We slogged onward and, the next afternoon, reached Nouamghar, a small fishing village where the dunes spill onto a treacherously narrow beach, the only route back to the highway, some 50 miles to the south. We woke at dawn to time our sprint with the three-hour low-tide window, barreling along at 60 until the Citröen dug in. We spent half an hour freeing it. With ten miles to go, the Rover got stuck; waves lapped at our feet as we furiously dug it out.

"Allez, allez, allez!" Hamid shouted. Five miles to go and bigger sets were slapping our tires. Then a mass of people materialized from the dust, diving out of our way. We'd made the highway. Fuzzy, who'd been driving, exited the Citröen and lit a cigarette. "Oh, God, that was dreadful," she said.

We hammered on to Mauritania's capital, Nouakchott, where Team Posh found a restaurant serving Heineken and, praise heaven, a passable plate of salty English chips.