Set in the 10th century. The Caliph of Baghdad, Al-Muqtadir, sends his ambassador, Ahmad ibn Fadlan, on a mission to assist the king of the Volga Bulgars. Ahmad ibn Fadlan never arrives, as he is conscripted by a group of Vikings, led by their chieftain Beowylf, to take part in a hero's quest to the north; he is taken along as the 13th member of their group to comply with a soothsayer's requirement for success. They travel to Hurot Hall, the home of King Hrothgar, to defend it from the 'mist-monsters', or 'grwendol', a tribe of vicious cannibal savages who go to battle wearing bearskins. After two devastating battles, Ibn Fadlan and the remaining Northmen decide to attack the Grwendol village, which is located in a network of sea caves. They infiltrate the sea caves, assassinate the head of the Wendol tribe, and return to Hurot Hall. Beowylf, however, is mortally wounded in the attempt. At Hurot, they encounter the Wendol in battle for a final time, defeating them. Ibn Fadlan is then allowed to continue on his journey.
