"He may not enter anywhere at the first, unless there be some one of the household who bid him to come"

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Creative Commons Attribution Share AlikeWelcome - Credit: Photofinish 2009
Though this may sound reassuring to us, a well-to-do Victorian household was full of servants and regular visitors (food deliveries, coal deliveries, etc), and the chances of unwittingly inviting a vampire in would have been much higher.

Though most later fiction tends to ignore this aspect of vampirism, some have played with it effectively; e.g. in Buffy the Vampire Slayer, a reverse spell can be performed in order to ‘change the locks.’