Carmilla's overall tone is mysterious, introspective, and sensitive. Le Fanu sets up the narrative through a frame story in which he presents Laura's story to the reader via the casebook of Doctor Hesselius. The novella is thus narrated by Laura, and her perspective significantly shapes the reader's understanding of the novella's events and characters. In general, the tone shifts throughout the novella reflect Laura's shifting emotions, especially during tense moments when she experiences fear and anticipation due to the danger posed by Carmilla's presence.
Carmilla's tone often reflects Laura's complex feelings of attraction toward Carmilla. Occasionally the tone is melancholy and reflective, especially during Laura's introspective moments when she ruminates on her experiences. The novella's tone notably shifts to become contemplative when Laura describes the fading landscapes of her childhood castle in Styria, conveying a sense of nostalgia and wistfulness to the reader. As Laura's emotions and private reflections unfold throughout the novella, the story's tone shifts in turn, allowing the reader to deeply empathize with what Laura is thinking, feeling, and remembering.
All in all, Le Fanu plays with tone in Carmilla to engage with the reader's emotions, making them all the more invested in the story's events. Because Carmilla is a work of Gothic fiction involving suspense, mystery, and tension, Le Fanu also uses tone to create similar feelings in the reader. Overall, the tone in Carmilla is a skillful blend mystery, suspense, melancholy, and terror. This multi-layered approach to tone contributes to the novella's captivating and haunting atmosphere, making it an enduring work of Gothic fiction.