In the spring of 1980, ambulance doctor Andrei Sergeev recorded a case of radiation sickness that affected one of his patients. How and when did the dying Soviet engineer become exposed to radiation, and why did state security become seriously interested in this case? Despite the fact that Andrei is preparing for his own wedding, he simply cannot refuse to participate in the investigation, not yet realizing the full seriousness of the case, the threads of which stretch far beyond the borders of Russia...