I am trying to find a book. Cannot remember the title or author, but I checked it out of the Newport News, VA public library when I was 11 or 12 years old (almost 40 years ago ... wow!). All I can remember is that its protagonists were a brother and sister. And the sister had silver hair - that was a big deal. And they traveled to another world and had a big adventure and then came back to the "real world." And the sister was sad about coming back. Good luck with this one! Thanks.