I can't figure out how Dracula controls Lucy and Renfield before he even sets out from Varna in Russia. How does he even know of their existence? I can just imagine that Jonathan somehow lets slip the name of his fiancee's best friend, but how would he even know of Renfield's existence, let alone be able to control him from a couple of thousand miles away? I'm assuming, of course, that the Lucy's sleepwalking and Renfield's fly- and spider-eating are somehow the result of Dracula's influence?
And while we're at it, what's Renfield for, anyway? As far as I can tell, he doesn't play any part in the plot, although he does commune directly with Dracula when he escapes from the asylum to Carfax.