The story has been cited as an inspiration for Lovecraft's "The Call of Cthulhu", which also features an extraterrestrial being who influences minds and who is destined to conquer humanity.

This anguish occurs for four days after he sees a "superb three-mast" Brazilian ship and impulsively waves to it, unconsciously inviting the supernatural being aboard the boat to haunt his home.

Throughout the short story, the main character's sanity, or rather, his feelings of alienation, are put into question as the Horla progressively dominates his thoughts.

Lettre d'un fou, translated into English as "Letter of a Madman", was published in the 17th February 1885 edition of Gil Blas, under the pseudonym 'Maufrigneuse'.

[6] It is likely that Maupassant was inspired by his own interest in hypnosis and psychiatry in writing the short story, having frequently attended the lectures of noted neurologist Dr Jean-Martin Charcot.

[7] The Horla's magnetic influence over the main character puts him in the same literary context as the double or doppelgänger, a field which had previously been explored in Adelbert von Chamisso's Peter Schlemihl (1814), Edgar Allan Poe's "William Wilson" (1839), and Theophile Gautier's Avatar (1856).

However, while in the traditional literary form of the double the perceived threat is a physical one capable of autonomy, in "The Horla" the titular creature is instead elusive and invisible, acting as a manifestation of the main character's solitude and anxiety.

[6] The ambiguity as to whether the eponymous Horla is an actual malign entity or a symptom of the narrator's mental illness is a key element of the short story's tension.

As the reader is not presented with information external to the protagonist that confirms any of the events of the short story, they are forced to reconcile with the possibility that the narrator is unreliable.

In the short story "The Theater Upstairs" (1936) by Manly Wade Wellman, the plot revolves around characters watching a film adaptation of "The Horla".

[1] In his survey "Supernatural Horror in Literature" (1927), he provides his own interpretation of the story: Relating the advent in France of an invisible being who lives on water and milk, sways the minds of others, and seems to be the vanguard of a horde of extra-terrestrial organisms arrived on earth to subjugate and overwhelm mankind, this tense narrative is perhaps without peer in its particular department.