Poe's masterfully written story is replete with macabre sounds and sights, terrorizing conditions, and bizarre people. After the narrator arrives at "the mansion of gloom," his sense of what he calls superstition heightens.
...a fancy so ridiculous, indeed, that I but mention it to show the vivid force of the sensation which oppressed me.
The narrator senses an atmosphere about the mansion that is nothing like any other; it is, perhaps, preternatural. When the narrator arrives at the Usher mansion, a "servant-in-waiting" takes his horse; then, he leads the narrator through a Gothic archway:
A valet, of stealthy step, thence conducted me, in silence, through many dark and intricate passages in my progress to the studio of his master.
And, as the narrator's "fancies" grow, the phantasmagoric occurs to the narrator as he traverses the dark hallway, perceiving strange images that blur his childhood memories of the Usher home. It is at this point that the narrator encounters the physician, who seems fearful and has an expression of "low cunning." This man is obviously uncomfortable around Roderick and Madeline, just as is the valet who tiptoes through the hallway. Certainly, there is something bizarre about the atmosphere in the house since the valet and physician seem to sense something as well as the narrator.
As if in confirmation of the bizarre atmosphere, the narrator meets his friend after so many years, and is taken aback by the changes in him, the "incoherence" in his character:
His voice varied rapidly from a tremulous indecision to...energetic concision....To an anomalous species of terror I found him a bounden slave.
That Usher distrusts the physician is evinced when he stows Madeline’s dead body in the vault because, as Roderick confides in the narrator, he fears the physician will steal the body and perform an autopsy on it in order to discover the causes of the family illness.
Apparently, there is a paranoia evident in Roderick, fears of discovery that may confuse and disarm the physician, who may feel the need to employ cunning, and cause trepidation in the valet. Their reactions to the Ushers, then, seems to confirm the apprehensions of the narrator that something strange and macabre exists in the House of Usher.