The battle lines are drawn – and only Timothy can cross them. Despite shunning Timothy since his arrival in Arcanum, the government has now turned to him for help. Raptus, the vicious leader of the dragon race called the Wurm, is determined to break through the magical barrier that separates his world from Sunderland and exact vengeance upon the mages. The Wurms need Timothy’s unique form of non-magic – his ability to invent things – to prepare for the inevitable battle.
Timothy sets out with his mentor, Leander, to the site of the barrier, but over the course of the trip Leander’s behavior evolves from erratic to dangerous – so much so that Cassandra is named Grandmaster of the Order of Alhazred. Can Timothy and Cassandra find the source of the Leander’s transformation before it destroys them all?