According to legend, a witch must have a cat. The heroine of the book, Ellen, has a Siamese cat, Ishtar. Ghosts appear in the house where she lives. One of the ghosts is the tragically deceased mistress of the house, who was considered a witch, the other is her Persian cat. Real and ghostly cats help the heroine understand who is a friend and who is an enemy, and then even save her from death. The habits of cats (and ghosts) are described with great love.