In Moscow, in the prime of his life, academic Nikolay Dolgonos dies. He is the director of one of the largest research institutes. Doctors diagnose an extensive heart attack, but the deceased’s sister Raisa doesn’t believe the doctors’ conclusion. She thinks her brother was killed for inheritance, and the killer is Dalvida—the young wife of the academic. Raisa turns to the well-known private detective Drongo for help. He agrees to investigate, understanding that most likely the doctors are right and the academic’s death is in no way connected to crime. But soon his attitude toward the case changes: a close acquaintance of Dolgonos dies under mysterious circumstances, and his professional instincts tell him it’s not just a coincidence…