The narrator is an articulate, educated man currently imprisoned and awaiting execution by hanging. He possesses a calm, analytical demeanor that masks his highly amoral and self-centered nature. Having calculated and executed the perfect crime, he lived comfortably on his inherited estate for years until an overwhelming psychological urge forced him to publicly confess. He views his own mind as a subject for objective study, using clinical language to describe his violent history.

The Imp is a supernatural personification of the human impulse to act irrationally and without control. Initially described as a theoretical spirit driving people to self-destruction, it takes on a confrontational form in the narrator's experience. It acts as an invisible fiend that actively harasses the narrator, eventually striking him on the back and forcing his ruinous public confession.

The murder victim is an educated man and a relative of the narrator, wealthy enough to leave behind an estate. He lives in a narrow, poorly ventilated apartment and maintains a consistent habit of reading in bed by candlelight. His predictable routine and enclosed living space provide the narrator with the perfect opportunity to replace his usual candle with a poisoned one.