The film is dedicated to the Bulgarian power industry. Buildings, turbine halls, control rooms of the Belmeken-Sestrimo-Klisura hydroelectric power station complex are shown; buildings, machine rooms, control panels of thermal power plants CHPP-1-Komsomolskaya and CHPP-Maritsa-Vostok-2, built according to Soviet designs; construction of the Kozloduy nuclear power plant; power lines. Soviet experts talk about joint work with Bulgarian colleagues (synchronously). The film tells the story of the Soviet Union's assistance to Bulgaria by supplying Donetsk coal and electricity via an electric bridge across Romania.