First published as a serial in The Dark Blue (1871–72),[1][2] the story is narrated by a young woman who is preyed upon by a female vampire named "Carmilla".

The story is popularly anthologised, and has been adapted extensively for films, movies, operas, games, comics, television, and other media.

[5] Le Fanu presents the story as part of the casebook of Dr. Hesselius, whose departures from medical orthodoxy rank him as the first occult detective in literature.

[6] Laura, the teenaged protagonist, narrates, beginning with her childhood in a "picturesque and solitary" castle amid an extensive forest in Styria, where she lives with her father, a wealthy English widower retired from service to the Austrian Empire.

Carmilla appears injured after her carriage accident, but her mysterious mother informs Laura's father that her journey is urgent and cannot be delayed.

Before she leaves, she sternly notes that her daughter will not disclose any information whatsoever about her family, her past, or herself, and that Carmilla is of sound mind.

When a shipment of restored heirloom paintings arrives, Laura finds a portrait of her ancestor, Countess Mircalla Karnstein, dated 1698.

In another nightmare, Laura hears a voice say, "Your mother warns you to beware of the assassin," and a sudden light reveals Carmilla standing at the foot of her bed, her nightdress drenched in blood.

He finds a small, blue spot, an inch or two below her collar, where the creature in her dream bit her, and speaks privately with her father, only asking that Laura never be unattended.

At a costume ball, Spielsdorf and his niece Bertha had met a very beautiful young woman named Millarca and her enigmatic mother.

The mother convinced the General that she was an old friend of his and asked that Millarca be allowed to stay with them for three weeks while she attended to a secret matter of great importance.

He hid with a sword and waited until a large, black creature of undefined shape crawled onto his niece's bed and spread itself onto her throat.

Afterwards, Laura's father takes his daughter on a year-long tour through Italy to regain her health and recover from the trauma, but she never fully does.

[8] In the novella, Le Fanu abolishes the Victorian view of women as merely useful possessions of men, relying on them and needing their constant guardianship.

[12] Le Fanu also departs from the negative idea of female parasitism and lesbianism by depicting a mutual and irresistible connection between Carmilla and Laura.

[16] The duality of Carmilla's character is suggested by her human attributes, the lack of predatory demeanour, and her shared experience with Laura.

This is evidenced by a report analysed by Calmet, from a priest who learned information of a town being tormented by a vampiric entity three years earlier.

Hall's account provides much of the Styrian background and, in particular, a model for both Carmilla and Laura in the figure of Jane Anne Cranstoun, Countess Purgstall.

Although Le Fanu portrays his vampire's sexuality with the circumspection that one would expect for his time, lesbian attraction evidently is the main dynamic between Carmilla and the narrator of the story:[25][26] Sometimes after an hour of apathy, my strange and beautiful companion would take my hand and hold it with a fond pressure, renewed again and again; blushing softly, gazing in my face with languid and burning eyes, and breathing so fast that her dress rose and fell with the tumultuous respiration.

Carmilla works as a Gothic horror story because her victims are portrayed as succumbing to a perverse and unholy temptation that has severe metaphysical consequences for them.

[27] Some critics, among them William Veeder, suggest that Carmilla, notably in its outlandish use of narrative frames, was an important influence on Henry James' The Turn of the Screw (1898).