I'm reading Bram Stoker's Dracula, and there are several passages where Miss Lucy is extremely ill, and resting in bed. During these occasions, there is very often a noise at the window, like something hitting it. The characters think that must be made by a big bat. I don't have the book in front of me right now, but IIRC these noises even occur on the nights Dr. Van Helsing and Dr. Seward are taking care of her.
Question: Is the noise begin caused by Dracula? If so, is he so dumb as to be struggling with a closed window, even when there are protectors nears his victims?
I am not through the whole book yet, but given its structure I don't think this issue is going to be explained.