Better than the cover would lead one to think!
King Edward of England is murdered by his stepmother and Satan, who is disguised as the courtier Angelo. This begins Angelo's plan to bring about a false apocalypse at the end of 999. To further his plans, he frees Loki to lead the Danes in "terror attacks."
Set against Angelo are two Witnesses--Alwyn, a crippled monk, and Kennag, a pagan Scotswoman. They are joined by a cat, a squirrel, a donkey, the ghost of Edward, and a faerie horse. Although Angelo does his best to stop them, they are able to ultimately defeat him by having Alwyn sing at Iona. Part of the reason for their success is that Loki sides with them after realizing Angelo set him up. Ultimately, Kennag returns home freed of inner demons and with the man she loves. Alwyn becomes one of the authors of the ASC and adopts Pangur Ban.