Topher and his father are trying to get over the death of Topher's mother, an Egyptologist, when they take in a stray cat. The cat bears an uncanny resemblance to a cat ornament given to Topher by his mother, so they name it "Ka," meaning "double." Topher becomes attached to Ka and is puzzled by her mysterious absences. One day, when he is playing an Egyptian-themed computer game, Ka jumps on the keys and spells out Bubastis—the center of cat worship in Ancient Egypt. Could Ka be leading a double life? What is she trying to tell Topher?