Lovely premise: a future galactic federation of ""United Faiths,"" whose constituent creeds have managed to parcel out the known universe among them in the manner of the Seven Sisters divvying up oil profits. Roused by news of rediscovered backsliders, the Church of Rome dispatches a redoubtable Jesuit to the godless planet of Charun to convert the erring and beat the Muslim Caliphate to the punch. Father Miles is an initiate of a brotherhood ""vulgarly called 'God's Brass Knucks' ""; once in the local palace, he dispenses threats, broken heads, and promises of longevity-drugs with a fervor that rapidly brings round a bright young gladiator and the sister of corrupt, degenerate Consul Ilya. Can Ilya be converted--say, to daisy food--before the Caliphate warship arrives to lay claim to the souls of Charun? Roberts steers his tale with high spirits and much inventiveness--but not, alas, with a reliable sense of shape. There's room here for a narrative half again as long, and this telling is simply too brief and perfunctory to do justice to a good idea.