Lydia Johnson is seventeen when the atomic bomb is dropped on Japan in 1945. Her family had just moved from the valley that later became known as Oak Ridge, Tennessee. In a vast undertaking called the Manhattan Project, the government took over the valley for the construction of the atomic bomb. In the summer of 1942, fourteen-year-old Lydia is mostly consumed with talking to her friend Willamena about boys and staying out of Mama’s long reach. The Johnsons gradually become aware of the government’s encroachment. Stranger Robert Doleman shows up and first disrupts their idyllic lives. When he and Lydia meet, he is the disinterested city guy; she is the outgoing but naive country girl. Lydia’s and Robert’s paths cross again after she and Willamena happen upon the aftermath of a violent crime.

The community is upset about the events, and Lydia is suspicious of Robert. As the community’s suspicion of the suspects turns to a couple of boys, Lydia begins to have romantic thoughts about Robert. The family's lives become even more disrupted as the children return to school and more strangers invade their peace. Finally, the family realizes that their life in the valley will never be the same as tumultuous events in their personal lives erupt and the government's invasion is complete.