1932. Ural, city of Krasnouralsk. The power plant has been sabotaged. The turbine is out of order. Having put the guards to sleep, someone poured sand into the turbine oil. In Moscow, the leadership of the OGPU received a secret cipher. From it it becomes known about the conspiracy of German intelligence against the USSR. Its main purpose — subversive actions in Soviet power plants. Special attention is paid to the Urals and the Dnieper under construction. Diversion in Krasnosilske — link in this chain. In Krasnotalsk sent a special agent of the OGPU Viktor Sergeevich Lartsev.

• Mystery