When the Bough Breaks — Mercedes Lackey; Holly Lisle

There are elves out there.

And they drive too fast. But they mean well. And they win races. But driving hot cars isn't all they do. Sometimes they rescue children in peril. But this time it isn't just the child who is in peril. This time we all are, because this abused little girl has more inherent psi power than anyone, mortal or elf, who has ever lived--and in her pain she might destroy Earth and Faerie both...when the bough breaks.