Ships suddenly began to die in Russian northern waters - in the most mysterious way. Having looked up the archives, specialists from the Federal Security Service found out that similar “epidemics at sea” occurred in the waters of the Barents and Kara Seas with a suspicious cyclicity - every six years. Moreover, it was not only our ships that perished. What happened all these years and continues to this day? Attacks by mysterious pirates? Or maybe this is some kind of paranormal phenomenon? Captain 2nd Rank Evgeniy Cherenkov, commander of an elite squad of combat swimmers, is tasked with starting a “hunt for the ghost”...