In the fourth decade of the twenty-first century, humans have been to Mars twice, but neither expedition successfully returned. Now, with worldwide interest in manned Mars exploration on the wane, a third expedition has made it by eking out resources from a combination of public and private sponsorship. But from the moment of their landing, everything begins to go wrong. The astronauts only hope of survival lies in trekking halfway across the surface of Mars itself a journey to the limits of human endurance.