The famous engineer Sergey Volgin developed the project for the Moscow Metro. His design was rejected by the Tsarist officials. However, the project didn't get lost among the millions of other proposals.

After the October Revolution, Volgin had to become an employee of the People's Commissariat of Food. However, the Bolsheviks tracked down the former engineer and offered him the opportunity to develop a new project for the Moscow Metro.

After Volgin's death, the work of his life is continued by his sons, Ilya and Alexander, who become tunnelers. The war breaks out, and their work is postponed.

The characters of the film had to endure much during the war years, but even in peacetime, the Volgin family faced complex life challenges.