This film tells a story spanning three generations, from 1871 to 1945. After the farmer's son, Gustav Wengler, returns from the Franco-German war in 1871, he goes to work in a precision mechanics and optical company. He soon becomes a master craftsman; he is loyal and devoted to this company and promises his director on his deathbed that his sons and grandchildren will also stand by the company. At last, the time comes for his talented grandson Paul to honor this promise and join the company. In the meantime, however, the company has gained a worldwide reputation and supports the Third Reich. Although Paul is skeptical about the Nazi leadership, he continues working for the company. When he sees the company destroyed during the war, old Gustav Wengler realizes his family is responsible for the turn the country has taken.