Sigwulf, a Saxon prince exiled to the court of Carolus, King of the Franks, is summoned by the royal advisor Alcuin of York. Carolus has received magnificent gifts from the Caliph of Baghdad and is determined to send back presents that will be equally sensational. White is the royal colour of Baghdad so the most important gifts will be rare white animals from the Northlands. Sigwulf, having proved himself as a royal agent to Moorish Spain, has been selected to obtain the creatures, then take them to Baghdad. He must find white gyrfalcons and two white polar bears and - as Carolus has seen its picture in a book of beasts - a unicorn. He and his companions travel far into the north. Though they obtain some of the animals, they quickly realize that not all are even real. Setting out for Baghdad with their menagerie, they encounter danger after danger and it seems that someone is trying to wreck their mission . . . with each stage of the long journey bringing a new and unexpected peril . . .