Theo Wilson time-travels back to 1889 to the bucolic river shores of Johnstown, Pennsylvania where the biggest flood in U.S. history is about to be unleashed. But how does the disaster happen? Wilson uncovers an elite, millionaires club that transforms the world's largest manmade lake into a personal playground for the posh by pushing aside much needed maintenance on the nearby dam. We discover how bad judgement and a passion for parties and fishing set the table for the tragedy, and learn what role the Transcontinental Railroad, heroic telegraph operators, and record rainfall play in creating a catastrophe that kills over 2,000 people.