Sirius the Dog Star has been convicted of the murder of a fellow luminary. As his punishment, he is sent down to earth to live as a dog, in which form he will die unless he can recover the mysterious Zoi.
With only dim memories of the star-world from which he has fallen, Sirius embarks on his seemingly impossible quest. Struggling to overcome the obstacles placed in his way by worldly as well as other-worldly forces, Sirius discovers that he must join the cold frosty hounds of the underworld in their midnight hunt. Only then can he make his request to their shadowy master.