A story spanning three generations, from 1871 to 1945. When Gustav Wengler, a farmer’s son, returns from the Franco-German war in 1871, he goes to work for a precision mechanics and optical company, where he soon becomes a master craftsman. Wengler loyally promises the owner on his deathbed that his sons and grandsons will also stand by the company.

When the time comes for his talented grandson Paul to honor this promise and join the company, it has gained a worldwide reputation and supports the Third Reich. Although Paul is skeptical about the Nazi leadership, he continues to work for the company. But when old Gustav Wengler sees the company destroyed during the war, he realizes that his family has contributed to the turn the country has taken.