Brendan is a twelve-year-old Irish boy who is the nephew of the Abbot of his village. Curious, imaginative, and intelligent, Brendan works for his uncle and the illuminators who serve him. One day, an elderly man named Aidan arrives with his cat, Pangur Ban, from a village destroyed by an evil horde of Vikings. Aiden takes Brendan under his wing and asks him to help work on a magical book he is creating, the Book of Iona. Brendan carries off his task, which is goes into a mystical forest to get berries to make the ink for the book. He is forbidden to go into the forest because the Abbot, Cellach, is building a wall around his village to protect it from the Vikings. When he enters the forest, Brendan makes friends with a forest spirit named Aisling. The story coonsists of Brendan visiting A