Sleep and Sleepwalking
Symbolism, Imagery, Allegory
In the world of Dracula, if you don't want to have your blood sucked you'd better down a lot of Red Bull... because being asleep tends to get you bitten.
When Jonathan Harker is staying at Castle Dracula, the Count warns Jonathan not to fall asleep in any room but his bedroom. When Jonathan falls asleep in another room of the castle, he almost gets bitten by the (super hot) Brides of Dracula. Lucy is an easy target because she sleepwalks:
Then, too, Lucy, although she is so well, has lately taken to her old habit of walking in her sleep. (6.39)
Once she's asleep, Dracula can influence her more easily and make her walk out of the house, where he can suck her blood. (Obligatory "Mwahahaha!")
Why are half-asleep people more easy targets? Well, obviously, sleeping people are less able to defend themselves physically. But their guard is down in other ways, as well. The novel suggests that almost everyone (even Mina and Van Helsing) have some kind of secret, deep-rooted desire to be bitten—they just keep it repressed most of the time.
But when they are half asleep, or sleepwalking, the desire bubbles to the surface. When asleep, their conscious minds aren't able to keep that naughty desire under wraps.
We'll give you a cookie and a copy of Freud's Greatest Hits if you can figure this one out... actually, it's if you can't figure this out that you should get your Freud on. This novel was written and set in Victorian England: possibly the most repressed era ever documented. Nobody wanted to admit that they wanted sexy sex sex. It was widely believed that it was only in dreams that your carnal desires reared their ugly head.