Book excerpt: Two alien races vie for the fate of Earth in Kathy Porter's thrilling sci-fi epic, Gray/Guardians. Wracked with environmental disaster and disease, humanity must decide whether to listen to the Grays, extraterrestrials who offer safe harbor on their planet, or the Guardians, who claim the Grays are using people as guinea pigs. The fate of mankind hangs in the balance in this chill-a-second novel.