A person wearing a hat and carrying a knapsack walks uphill on a sand dune under a dark , cloudy sky and leaves the only visible footprints behind .
It is impossible that a man is trying to hitchhike his way across a desert .
It is impossible that a man is trying to hitchhike his way across a desert .
Chances are about even that a man is trying to hitchhike his way across a desert .
A man is trying to hitchhike his way across a desert .