The western Sahara is a baking hot and desolate place, home only to nomads and their camels, and to locusts, snails and thorny scrub - and it has a barren and ever-changing coastline has baffled sailors for centuries. On 28 August 1815 the US brig Commerce was dashed against Cape Bojador and lost, although through bravery and quick thinking the ship's captain, James Riley, managed to lead all of his crew to safety. What followed was an extraordinary and desperate battle for survival in the face of human hostility, hunger, dehydration and despair, as the crew were captured, robbed and enslaved. Sometimes together, more often apart, the sailors were dragged or driven through the desert by their new owners, who neither spoke their language nor cared for their plight. Reduced to drinking urine (their own and the camels'), flayed by the sun, crippled by walking miles across burning stones and sand and losing over half of their body weights, some of them nevertheless held on to their sanity. And over time James Riley and Sidi Hamet, slave and captor, came to recognize in each other men worthy of respect and the ransom not only of Riley himself but also of a handful of his crew suddenly seemed possible. But Sidi Hamet had enemies of his own, and to reach safety the sailors and their saviour had to overcome not only the desert but also the greed and anger of those who would keep them in captivity.