It's the ultimate test of endurance- two-hundred-and-fifty miles in the brutal heat of the Sahara, with only the supplies you can carry on your back.

Adri is ready. Returning to ultra-running in the wake of a scandal, she needs to prove to herself - and her young son - that she's a winner.

When a fellow runner is badly injured, Adri knows something isn't right. Yet in a race this extreme, even a dead body can be explained away.

But there's a killer stalking the hot sand. And the problem with running faster than everyone else, is that you're miles ahead of anyone who can save you...