This question already has an answer here:

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.

marked as duplicate by Shevliaskovic, Ward, Often Right, Moogle, Anthony Grist Sep 16 '14 at 10:34

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.