The Silver Crown — Robert C. O'Brien

Ellen awakens one morning with a mysterious silver crown on the pillow beside her. What magic powers it possesses she has not yet discovered, but the sudden changes in her life are unmistakable; her house is burned down, her family has disappeared, and a man in a dark uniform is stalking her. Can Ellen ever find her family? Can she use the power of the silver crown to thwart the powers of darkness? What diabolical force hides inside the mysterious castle in the woods?