This is the 5th adventure in the Sandra Swift adventures. A criminal organization is systematically stealing plutonium from nuclear power plants and laboratories all over the United States. While a nationwide investigation goes on, concerns are rising that the next target will be the Citadel: the atomic research facility built and operated by Swift Enterprises. Tom Swift Sr. is confident that the Citadel's security will be sufficient to defend it, but he's soon proven wrong as the thieves strike. Not only is plutonium stolen, but it's suspected that the thieves are also linked to the murder of an Enterprises robotics scientist. Suspicions point to someone working within the Swift organization. A resourceful individual who remains behind the scenes, and who can outthink even the brilliant minds operating the Citadel. And Sandra Swift soon finds herself facing her most dangerous and calculating opponent.