A Tiger's Heart by Lauren Wright Douglas 1992, Paperback
"She's dead," Jory tells Caitlin. "My mom is dead."The police find no body. And suspect only ten-year-old Jory's overactive imagination. But Jory knows what she saw, and, chillingly, what she wants Caitlin to do: find Kirk Ratliffe, her monstrous father, and kill him. Caitlin cannot conceive of what she will face.