In the year 133 AD: Thousands of Roman legionnaires guard the border to Germania in the province of Raetia. Suddenly, something sinister happens at the fort of Vetoniana: more and more soldiers are struck by a mysterious illness. Have they been poisoned? Germanic traders, who live peacefully on the other side of the Limes, come under suspicion. Roman boy Magnus and his friend Finn from Germania refuse to believe this and decide to investigate on their own. They sneak onto the estate of a wealthy landowner and overhear the "Operation Satan's Mushroom." A dangerous race against time begins.