Time-travelling Cat and the Egyptian Goddess

Topher and his father are trying to get over the death of Topher's mother, an Egyptologist, when they take in a stray cat. This cat bears an uncanny resemblance to a cat ornament given to Topher by his mother and so they name it 'Ka', meaning 'double'. Could Ka really be leading a double life and what is she trying to tell Topher?