* Focus on the characters' mental states: The story centers around the protagonist's growing unease and suspicion as he interacts with the landlady. The reader is also made to question the reliability of the protagonist's perceptions.
* Unreliable narrator: The protagonist is presented as a relatively naive and trusting young man, making his judgment and perception of the landlady unreliable. This creates suspense and makes the reader wonder if his suspicions are warranted.
* The mystery is rooted in the psychological: The main tension doesn't come from a physical threat or a crime that has already been committed. Instead, the unsettling atmosphere and the landlady's strange behavior create a psychological sense of dread and unease.
* Open to interpretation: The ending of the story is ambiguous, leaving readers to draw their own conclusions about the landlady's true nature and the protagonist's fate. This ambiguity adds to the psychological impact of the story.
While there are elements of suspense and a mysterious atmosphere, the story's primary focus is on the protagonist's mental state and the unsettling interactions with the landlady. This makes it a classic example of a psychological mystery.