In the second book of the series, Andy and Mark race home from the baseball field and discover that a mystery intruder has activated the time machine! Worse than that, the intruder has traveled back in time and changed history the United States is gone! The new world is mired in violence and the population has no hope. The boys mission is clear. Find out what happened, return to the past, and stop the person that disrupted the time line. But the new world has some surprises, and the task proves harder than it sounds. Follow along as Andy and Mark befriend a local teenager, dodge the secret police, and participate in one of the key battles of the American Revolution!