[Stranger with My Face] is one of Duncan's sleazier supernatural thrillers, which doesn't mean that it won't find its shiver-seeking readers. It's told, with appropriate shudders and foreshadowing, by 17-year-old Laurie Stratton, whose senior year of high school on a remote New England island is haunted by (she learns midway) a twin sister left behind when Laurie was adopted as an infant. First, others report seeing Laurie where she wasn't—a boyfriend breaks with her because of the assumed deceit—and at last twin Lia, identical except for those evil, malevolent eyes, reveals herself to Laurie. Laurie's parents confirm the adoption, the twin, and the fact that the girls are half Navaho; and Helen, a new school friend from the west, explains to Laurie about astral projection—a talent more common among the Navaho, who can leave their bodies to travel at will. Laurie masters the technique herself...