First published as a serial in The Dark Blue (1871-72), the story is narrated by a young woman preyed upon by a female vampire named Carmilla, later revealed to be Mircalla, Countess Karnstein (Carmilla is an anagram of Mircalla). The character is a prototypical example of the lesbian vampire, expressing romantic desires toward the protagonist.

The novella notably never acknowledges homosexuality as an antagonistic trait, leaving it subtle and relatively unmentioned. The story is often anthologized and has been adapted many times in film and other media.