Twin sisters Destiny and Livvy Weller return home from summer vacation with a dark secret . . . and an inhuman desire to drink blood. What have they become? Can they ever turn back? As their deadly secret becomes harder to keep, more questions arise and loyalties are tested. And as one sister descends into darkness, the other must find a way to save her—and herself. Who will live to see the glow of the next full moon? Which sister will survive? In and , published together in , bestselling author R.L. Stine explores the dark creatures of the night.