And the darkness brought with it a word of warning.  While in one sense it was a protection, on the other it had in it an element of danger. He could no longer know the direction in which he was traveling.  He knew the danger there was of traveling in a circle.  If he kept on he might swing around in the direction of the German lines.  And it would be a sorry ending to his flight to have it finish at the very point from which he had started.