It is a time of civil war. The power-hungry Macbeth has murdered King Duncan and proclaimed himself King of Scotland, but powerful forces oppose Macbeth and the country is plunged into a conflict it may not survive. To ensure his continued dominion, Macbeth seeks the Codex Diabolus; an ancient and mystical text which promises unlimited power to whoever can uncover its secrets. Gavin Hamilton, a young monk of the wealthy and prestigious Fortrose Abbey, is swept up in the drama and intrigue as he tries to keep the Codex from falling into Macbeth's hands. But to do so he must traverse the haunted and forbidding Birnam Wood; a place where things are never what they seem. It is in Birnam Wood that Gavin is forced to examine his most closely held beliefs while being hunted by the ruthless and murdering Macbeth.