In a shocking act of domestic terrorism, a deranged veteran detonates a biological weapon inside a crowded Federal Building. His purpose: To expose the government's secret development of a toxic gas that instantly affects the human adrenal system, causing men, women and children to become inhumanly aggressive and violent. Now the virus is spreading. The building is quarantined. And on the upper floors, a small group of uninfected survivors must band together to get out alive.