When the dog star Sirius is falsely convicted of murdering a luminary, Polaris sentences him to a real dog's life on earth, where he becomes the pet of mistreated little Kathleen--and there's much well-staged action in their run-ins with the family she lives with and in Sirius' rocky road to accommodation with their cats. But it's to be a dog's death too unless Sirius finds something called the Zoi--even he doesn't know what it is, but he recognizes its awesome power when he does acquire it, after much frantic to-do: urgent consultation with Sol and Earth, a midnight hunt with a horned hound master, and some hair-raising encounters with his treacherous former Companion, now in human form but retaining her eerie luminosity. And so Sirius ends up back in his sphere and Kathleen, through his intercession, in a kinder home. Jones sees clearly and writes effectively and the girl-and-dog story is a sure, and never sticky, heart-tugger. But the cosmic trappings are merely ridiculous.