Tony Stark is accused by Defense Minister Kuroda of trying to avoid controversy by sneaking plutonium into Japan aboard an undefended cargo ship. This ship has been attacked and the plutonium stolen, posing a grave threat. Tony dons the Iron Man armor and vows to retrieve the plutonium and clear his name.

When the Arc Station has a series of malfunctions, Tony and Dr. Tanaka discover a Zodiac computer virus has infected the Station's operating systems. The virus spreads to the city's ATM banking computers, train navigation computers and traffic controls, causing chaos. Tony decides the only way to combat the virus is to draw it to another computer... his Iron Man onboard computer!

The plutonium needed to prime the Arc Station is stolen and Tony must don the Iron Man armor and fight against Dio. The two Iron Men must fight to the death, with the fate of Japan hanging in the balance.

Tony Stark learns the shocking truth behind Zodiac. Iron Man must muster all his remaining strength in order to stop the nefarious ambitions of his greatest adversary, the man behind Zodiac. But, when an familiar face enters the battlefield, will he be able to do what needs to be done?