The story is based on an alternative history of the events of the Cold War. Until the 60s of the last century, these events were similar to the official chronicle, but then the river of history suddenly changes its course. Saboteurs from Western intelligence services are importing into the USSR a strain of an unknown virus that is similar in impact to Covid-19 or the Spanish Flu, and is significantly superior to them in the rate of infection. Most of the adult population of the Union dies from this virus within a few weeks. As a result, the territory of the USSR is declared a quarantine zone, and as one of the isolation measures, a high wall with a length of about two thousand kilometers is being erected on the western border of the Soviet Union. For the next fifteen years, the wall is guarded by a special paramilitary unit of the German army on behalf of whose representatives the story is told.