The Johnstown Flood (1926)

Tom O'Day is loved by two women, Anna Burger and Gloria Hamilton. Tom has no idea of Anna's love for him, and he becomes engaged to Gloria. Gloria's uncle, John Hamilton, is a wealthy lumber man who controls a dam upstream of the town of Johnstown, Pennsylvania. He wants the water behind the dam kept at the highest level in order to facilitate his logging contracts. But Tom knows that the dam is faulty and endangers thousands of people in the valley below. A massive flood seems inevitable unless Tom can convince Hamilton to allow the floodgates to open and reduce the danger.