In the prologue of A Game of Thrones it is described how Gared runs for his life, when he and other two rangers encounter with White Walkers. But this happens north of the Wall.
In the first chapter, we find Lord Eddard executing him outside the walls of Winterfell. Hundreds of miles south of the Wall.
How did Gared get through the Wall? Is this a plot inconsistency? He can't have deserted the Watch after reporting the incident. If he did Night's watch would have known about the White Walkers.
