Leningrad, winter 1952. An invisible killer known as Koshchei - a nightmare of Slavic folklore - stalks the streets, leaving a distinctive and gruesome mark upon its victims. Three thousand kilometres away in a Gulag labour colony, threatened by the vicious criminals who rule the camp and tormented by the Arctic cold, former militia lieutenant Revol Rossel is close to death.

But then a brutal saviour descends from the skies: the state security interrogator who years ago ruined his life is back, tasking Rossel with tracking down the murderer. As the hunt continues, the two men uncover riddle after riddle, including a clue to finding a weapon of unimaginable power - a weapon the Kremlin's scheming plotters will kill for...