Fifteen-year-old Bobby Hastings witnesses an atomic explosion near a top secret New Mexico army base in July of 1945. Terrified, he soon heads off on his bike for home, only to encounter something that rivals the blast for drama. A girl his age stands naked at the side of the lonely desert road: underweight, unwell, and speaking with a German accent. In the coming days, she unveils an impossible story about time travel and a heartbreaking outcome of the war. She begs people to believe her warning and prevent the awful future she claims to know too well. But even if they do believe her, and the story is true, the biggest question remains: can history be undone?