"How dare you touch him, any of you? How dare you cast eyes on him when I had forbidden it? Back, I tell you all! This man belongs to me! Beware how you meddle with him, or you'll have to deal with me." (3.34)
Dracula doesn't try to hide that he's in control, does he? He actually claims ownership of Jonathan.
[…] there was that in his eyes and in his bearing which made me remember that I was a prisoner, and that if I wished it I could have no choice. The Count saw his victory in my bow, and his mastery in the trouble of my face […] (3.15)
Jonathan is powerless in Castle Dracula. Look at the language he uses! He knows that the Count has "master[ed]" him.
I closed my eyes in a languorous ecstasy and waited—waited with beating heart. (3.32)
Even as he's about to be kissed/bitten by the sexy vampire, Jonathan remains passive and still.
The sight seemed to paralyse me […] (4.62)
The very sight of Dracula's face, even as he's sleeping (or whatever it is vampires do), is enough to "paralyse" Jonathan.
Then, too, Lucy, although she is so well, has lately taken to her old habit of walking in her sleep. (6.39)
Lucy's habit of sleepwalking makes her vulnerable to Dracula—it puts her in a state of semi-conscious passivity.
Lucy has not walked much in her sleep the last week, but there is an odd concentration about her which I do not understand; even in her sleep she seems to be watching me. She tries the door, and finding it locked, goes about the room searching for the key. (6.41)
Lucy's passivity while she's sleepwalking makes her easy for Dracula to control.
Mina Murray Harker
It is a very strange thing, this sleep-walking, for as soon as her will is thwarted in any physical way, her intention, if there be any, disappears, and she yields herself almost exactly to the routine of her life. (7.30)
Lucy is so passive while sleepwalking that Mina is able to redirect her easily enough—as long as she does so physically.
"I am here to do Your bidding, Master. I am Your slave, and You will reward me." (8.38)
Renfield submits himself entirely to Dracula. It doesn't work out so well for him.
All the resolution has gone out of his dear eyes, and that quiet dignity which I told you was in his face has vanished. (9.1)
Because Jonathan is full of self-doubt about what happened in Transylvania, he becomes irresolute and indecisive.
Mina Murray Harker
I would have got out to make certain on the point, but some leaden lethargy seemed to chain my limbs and even my will. I lay still and endured; that was all. (19.39)
As Mina is having her blood sucked for the first time, she finds a kind of "lethargy" or passivity creeping over her.