Twelve-year-old Elvis Babbitt has a head for the facts: she knows science proves yellow is the happiest color, she knows a healthy male giraffe weighs about 3,000 pounds, and she knows that the naked mole rat is the longest living rodent. She knows she should plan to grieve her mother, who has recently drowned while sleepwalking, for exactly eighteen months. But there are things Elvis doesn't yet know--like how to keep her sister Lizzie from poisoning...