“I had to stop her from going to prom,” she said, her voice small but firm. It was the voice she used when she knew she was in trouble but was utterly convinced of her own righteousness. This was my baby, the little girl who still crawled into her big sister’s bed during thunderstorms, who followed Kayla around like a shadow. I couldn’t fathom the malice it would take for her to sabotage the most important night of her sister’s life.