Among the arrivals are Sadowsky, a hydroengineer sentenced to 10 years for sabotage, and Kostya-Captain, a repeat offender and leader among the criminal inmates.
Kostya-Captain initially disrupts the camp's operations by discouraging labor, undermining the "shock construction" project and its rehabilitative objectives.
The camp administration employs a combination of tact and persistence in their efforts to rehabilitate prisoners, presenting Soviet power as humane and reform-focused.
Kostya-Captain is eventually appointed head of an expedition to raft timber for the construction project, receiving weapons on a signed receipt for the task.
In the final scene, the steamship Karl Marx navigates the locks of the Povenets Staircase on the completed White Sea–Baltic Canal.