A week has passed since Jon, Pete, and Abby returned home from the attack on Pearl Harbor. Now all they want is to relax and enjoy the remainder of their summer. However, they soon realize that their time-travel adventure has just begun. After noticing minor changes in their neighborhood's landscape, and receiving a cryptic phone message from an unknown source, the Brewster boys and Abby realize that something is missing from America - the states The Mississippi River now divides the United States and the North American territory of the Soviet Union Feeling responsible for these radical changes the Brewster boys and Abby have no other choice but to travel back and set things right. On their journey they'll discover significant changes in the events of the Manhattan project, the Cuban Missile Crisis and the assassination of J.F.K. They will even visit Nikita Khrushchev's Moscow