SOLVED. YA Fantasy: Cave to another dimension. Waterfall? Kidnapped sister. Fantasy-world strategy mirrors real-world game. [s]

[Carolyn]

Its main character is a girl probably named Emma or Emily, who has a very pale face and white hair. She finds out she's from another world/dimension when she accidentally gets there through a cave with a waterfall. She also discovers that she's not the biological child of her 'earth' mother, but of royalty (I think) from the other world, which explains her abnormal colouring.

I think that the ocean, beaches and/or sky were not a normal colour in the other world. I think there was more than one moon in the sky.

The villains are trying to kidnap the main character's sister, who might have been named "Summer", because they're part of a war to determine who's in charge of her real, royal parents' realm in the other world.

I could VERY easily be wrong about this, but I think that the actions of the characters in the other world are governed by the rules of a sort of strategy game - i.e. the villains can't make a move until the good guys have made one.

Early in the book, she meets an old man who turns out to be from the other world. I think the man owned a root cellar, and I believe they played a game much like chess, and that the rules of that game mirrored the rules the people of the other world had to follow (see end of my previous paragraph).

Fairly early in the book she gets sunstroke.

I'm pretty sure this was the first in a series. Oh, and it could easily be a children's novel rather than YA novel - I read it in elementary school. I read it in the '90s.

[D.M.]

This would be The Watcher I believe

[Cheryl]

It sure does look like it. Looks like the other two books in the trilogy are better, too.

[Carolyn]

Yay! Thank you, that's it!