How would you describe the setting, atmosphere, and character development in "The Horla" by Guy de Maupassant?

Maupassant’s 1887 horror short story "The Horla" is written in the form of journal entries. The setting is the narrator’s large estate in the country outside Rouen, France. The atmosphere is one of increasing anxiety and unease over four days as the narrator notices strange occurrences that begin when he waves at a Brazilian boat. This seemingly innocent act ushers in an evil presence the narrator calls the Horla. The atmosphere progresses from tense and agitated to hallucinatory and desperate.

The character development of the narrator causes the reader to question his reliability. At first, the evil presence manifests in the form of physical complaints—fever, restless sleep, the feeling of being watched, the sensation of someone kneeling on his chest. The narrator himself questions his sanity as the Horla consumes his thoughts. Whether or not the reader agrees, the narrator concludes that he is sane but continues to feel threatened by the supernatural Horla. The narrator reads an account of strange phenomena in Brazil where people are being terrorized by supernatural creatures and realizes the origin of the creature that brought his suffering. The narrator attempts to cast out the creature by burning his own home and even considers suicide if that would destroy the evil being that may be inside him. This character development relates to themes of questioning reality, perception, and sanity.