“Desert Odyssey” (Part 2 of eight) follows Adam Ilius, a 9-year-old boy from Niger, on his first caravan across the Sahara, a six-month, 1500-mile trek along “camel superhighways.” Of course it's dangerous. “No one goes into the desert unless they have to,” says narrator Joe Morton. The purpose of the caravan: to buy and sell salt, and these days there's competition from trucks. The hour also explores the Sahara's “secret past” (6000 years ago it was a grassland) and surveys the wildlife along the way. Life isn't easy for scorpions and hyenas. And for birds, “the maggots on a dead camel are a feast.”