Gunman's Reckoning by Max Brand

But even though this major step was accomplished successfully, Lefty Joe was not the man to abandon caution in the midst of an enterprise. The roar of the train would have covered sounds ten times as loud as those of his snaky approach, yet he glided forward with as much care as though he were stepping on old stairs in a silent house. He could see a vague shadow -- Donnegan; but chiefly he worked by that peculiar sense of direction which some people possess in a dim light. The blind, of course, have that sense in a high degree of sensitiveness, but even those who are not blind may learn to trust the peculiar and inverted sense of direction.

With this to aid him, Lefty Joe went steadily, slowly across the first and most dangerous stage of his journey. That is, he got away from the square of the open door, where the faint starlight might vaguely serve to silhouette his body. After this, it was easier work.