Fear in a Handful of Dust

Two people have to deal with the death of the world around them as they walk along the shoreline of a decaying wasteland. On top of being tired, hungry and thirsty they struggle to find a reason to keep going as there doesn't seem to be much except them left in the world. The only other sign of life is a mysterious figure that is constantly closing in on them. The purpose of the figure is unclear but the two survivors desperately try to keep their distance.