In Pervert's Guide to Cinema (2006), Zizek reads the attacks of the birds in The Birds (1963) as externalized maternal superego. Count Orlok's attack on Hutter's wife Ellen at the end of Nosferatu (1922) functions in a similar way. At the beginning of the film, Hutter is sent to Transylvania to talk to Count Orlok about buying property in Wisborg. He stops at an inn on his way and discovers a book about vampires, which begins to function as his and the audience's fantasy frame to explain the presence of Nosferatu. While he is out of town his wife stays with his friend Harding who Hutter becomes jealous of, symbolized by the obvious vampire bite on his neck (which he explains away as mosquitoes) and by his writing to Ellen while he is gone despite the fact that he is only supposed to be away for a few days. He then confronts Count Orlok, now in the form of the “Bird of Death”, the external embodiment of his jealous superego, and he falls unconscious. It is noteworthy to mention that Orlok/Nosferatu does not kill or even attack Hutter (at least in the way he later attacks Ellen) since it is traumatic for him to encounter his unconscious desire, but not deadly. Orlok/Nosferatu and Hutter eventually make it back to Wisborg, and Hutter (unconsciously) gives Ellen her final test: he tells her not to read the book about vampires Hutter took from the inn (which of course would make no sense if there was a real vampire on the loose, since he would want her to be prepared, but makes perfect sense in the interpretation of the book as his fantasy frame, one of his most intimate secrets) which she does anyway. By failing this test Hutter knows Ellen has been unfaithful (symbolized by Nosferatu entering her bedroom while she's there alone), or at least that she can no longer occupy the position of objet a for him (since she knows his fantasy & betrayed his demand/desire), and Orlok/Nosferatu/Hutter's jealous superego kills her.
While it could be possible to argue that there is an actual vampire loose in Wisborg as evidenced by the deaths around town, these deaths are perfectly accounted for in the movie: plague.