It’s long been the stuff of nightmares for America’s top homeland-security officials. Well-trained terrorists assault one of the nation’s nuclear-power plants, nearly a dozen of which are near major metropolitan areas. The militants kill the facility’s private-security guards and make their way to the plant’s reactor. Federal law-enforcement personnel rush to the scene, but it’s too late. The terrorists trigger a full-scale nuclear meltdown, killing tens of thousands of people and rendering nearby cities uninhabitable for decades.