Just Another Dream?
The frames on this page are cropped the same amount as those on the previous page, but instead of cropping equally on both sides, I've taken everything from the left so we don't miss Gandalf's movements.
We don't see a lot of change in Frodo. If anything, he seems to trust what he's seeing even less than he did on the previous page. He gradually moves his left hand farther back so he has more stability and leverage, and in or about frame 17 his expression goes from blank to fearful. (The change of expression is a natural continuum; I picked #17 because that's where the eyebrows get involved.)