Heartlight

Kate is a teenage girl living with her astrophysicist grandfather in New England. When her grandfather's research attracts unwanted attention from an otherworldly visitor, he mysteriously disappears. Kate must rush to find him - and the secret that can save the Earth and the entire solar system from annihilation - before it's too late. "One of the best Science Fantasies I've read in a long time."-Madeleine L'Engle