The unnamed narrator shares a home with an elderly man and claims to possess overly acute senses, particularly an exceptionally sharp sense of hearing. Despite expressing affection for the old man, the narrator develops a severe fixation on the man's cloudy, pale blue eye. This fixation drives the narrator to carefully observe the old man while he sleeps, motivated by a dark desire to permanently rid the house of the visual trigger. The narrator's behavior is characterized by extreme caution, stealthy nocturnal movements, and an obsessive need to prove their sanity to the audience.

The old man is an elderly, seemingly wealthy individual who shares a residence with the narrator. He possesses a pale blue eye covered by a thick film, suggesting he suffers from cataracts or partial blindness. He is entirely unaware of the narrator's nocturnal stalking and the severe distress his eye causes his housemate. He generally trusts the narrator, having never wronged them, but he experiences profound terror when awoken by sudden noises in his dark room.

A group of three law enforcement officers who visit the residence after a neighbor reports hearing a scream during the night. They conduct a routine search of the premises to ensure no foul play has occurred. They are agreeable and easily satisfied by initial appearances, sitting down to rest and chat once the physical inspection of the house yields no immediate signs of danger.