Madeline and Sophie Ryan are identical twins. They are eight years old. They exude a rugged masculinity and are built like their merchant marine father — thick, solid, broad shouldered, with eyes so dark and glassy they seem to be made from perfectly polished pieces of obsidian. Mass murderers of spiders, flies, moths, and the exceptionally brilliant brush-footed butterflies that sail above the surface of the family swimming pool, the girls constantly hunt for easy prey. They’re also accomplished mimics who delight in doing impersonations of adults, aping their vocabulary with unnerving precision in a single singsong voice and then…