Oh, what fun biology students have in practice! This is not for you to pore over test tubes. Teacher Svetin's students frolicked peacefully on the Chulymka River, celebrating the first day of field testing. And suddenly, from the opposite bank, shooting began... at the boys, who were stunned with horror. The guys miraculously managed to escape, only one was caught. But teacher Markov was much less fortunate: he was found shot in the head. The gun of Svetin, who had been hunting an hour earlier, was thrown next to the corpse. His son, realizing that his father was cynically framed, turns for help to a professional bodyguard and detective rolled into one, Evgenia Okhotnikova. Moreover, the list of victims is growing and the children of the unjustly convicted professor are first on it....