There are elements of both fantasy and more factual elements in this story. Clearly the phenomenon of stealing bodies from graves was a common practice in Victorian times, and the so-called "Resurrection Men" whose job it was to illegally take bodies from newly dug graves are a historical truth, that Dickens himself used in his novel A Tale of Two Cities. However, clearly what Stevenson in this story does is to add a somewhat gothic twist to the ending, where there is a mysterious reappearance of a body that was dissected into pieces and therefore conveniently destroyed. The "crime" appears to be a perfect one, and Fettes excitement and pleasure at how he witnesses all of the evidence being eroded in front of his eyes in the following quote:
For two days he continued to watch, with increasing joy, the dreadful process of disguise.
This story, however, seems to suggest that no matter what attempts are made to conceal or to "disguise" sins, crimes will come back to haunt the perpetrators. This is where the element of fantasy enters the story, as, instead of a dead woman, they dig up the corpse of what appears to be Gray. Of course, the setting of this scene in the dark graveyard at night with just Fettes and Macfarlane adds a certain amount of doubt to the account: is this just their guilt getting the better of them? The dramatic way in which they jump from the carriage and leave "the body of the dead and long-dissected Gray" as the "sole occupant" as it rushes towards Edinburgh gives it a strong fantastical element, but there is enough doubt to question the veracity of this account. Stevenson deliberately blends fantasy and fact in this story in order to shock and disturb his readers, producing a very pleasing gothic story. It is thus impossible to classify this story as either fantasy or fiction: it is definitely fiction, but Stevenson produces something of a gothic ghost story that successfully blurs the boundaries of classifcation.