The Hammer and the Cross is a science fiction novel by Harry Harrison and John Holm, a pseudonym for the Tolkien scholar Tom Shippey. The first in a trilogy, the book chronicles the rise of Shef, a bastard son of a Viking and an English lady. The book is alternative history set in 9th century England, where Viking raids are common. In this tale, the authors explore what might have happened if the Vikings had fought more successfully against the rule of Chalcedonian Christianity. Central to this story is the protagonist Shef. In the story, Shef's birth is discussed. Such as if Shef is the son of the Norse god Ríg, or of a Viking named Sigvarth. More widely, the story questions whether Shef's visions are messages from the gods or dreams. These questions are developed through the trilogy. Source: Wikipedia (en)