Nightshade — John Saul

Fifteen-year-old Matthew Moore seems to have a charmed life...until a mysterious fire forces his grandmother to move in with his family. The elderly woman insists on re-creating the bedroom of Cynthia, her favored child who died tragically more than a decade ago. Soon Matts life insidiously begins to change. At night he finds himself haunted by nightmares of unimaginable terror. In the morning the smell of Cynthia's perfume seems to linger in his room. While his grandmother drives a wedge between his once devoted parents, Matt transforms from a gregarious teenager to a hostile loner. Then a shocking tragedy shatters the family beyond repair--as a horrific shadow from the past takes on an implacable life of its own, clawing toward Matt with ferocious hunger....