]Isabella catches hold of one of Catherine's hands and Thorpe the other to stop her from doing so.

I didn't remember that they actually grabbed her to keep her from leaving. A parody, perhaps, of the abduction of the heroine in a typical gothic novel, but another way of JA making her point that the Thorpes are not fit company for her. I'm with you on James: what was he thinking in allowing his sister to be treated like this?! It made me wish Colonel Brandon would show up, pistol in hand . . . ;-D But Catherine will be in the company of my second favourite Austen hero in due time, so I will try to wait with patience.