Do you mean this?
Valanice dreams that she is a prisoner in the tower, but Graham enters her dream and rescues her, so in the end it's a good dream. Perhaps Graham is fulfilling Lady Maab's promise by entering her dream and turning it into a good dream.
I think that that's the main part of Graham's quest in TSL, to enter Valanice's, Alexander's, and Rosella's bad dreams and turn them into good dreams. Because, with all they've been through, bad dreams are the principal demon that is haunting them.