The author's concern in this memorable tale is to present us with a taut psychological drama that narrates an incredible, fantastical escape compressed into the last few seconds of Farquhar's life before he is executed by hanging. Therefore, to help communicate that this is all a fantasy, the author uses a variety of different point of views in the tale but also within his account points to the unreality of the situation by making the description seem mysterious and strange.
If you follow the narration through the tale the point of view shifts variously from omniscient narrator, objective narrator to finally third person limited narrator, as we follow the action from Farquhar's point of view. Particularly when he focuses on Farquhar's flight of fantasy as he escape, the point of view that is selected to narrate this section of the story is third person limited, as it helps the narrator to maintain a realistic perspective on the action, even as Farquhar's mind delves ever more into the realms of fantasy.
However, the author plants clues or hints that what is happening is not real. Consider the description of the territory around Farquhar's home towards the end of the novel:
At last he found a road which led him in what he knew to be the right direction. It was as wide and straight as a city street, yet it seemed untravelled. No fields bordered it, no dwelling anywhere. Not os much as the barking of a dog suggested human habitation. The black bodies of the trees formed a straight wall on both sides, terminating on the horizon in a point, like a diagram in a lesson in perspective. Overhead, as he looked up through this rift in the wood, shone great golden stars looking unfamiliar and grouped in strange constellations.
Note here how this effectively foreshadows the ending. Because we see the landscape through Farquhar's eyes, we would expect it to be familiar, since he is not far from his home. However, the scene has a surreal, nightmarish quality that indicates that something is not right.
Therefore, if you are going to comment on the narrator, two areas to think about referring to are the shift in the point of view and the way that description is used to indicate the fantasy that we are shown.