One quite morning fishermen find headless body by the river. It is the third cruel murder in this area that allows to call it a spree. Two detectives despite mutual antipation and frequent conflicts, start the investigation. Is it true that serial killer is the main culprit of what happens in town or somebody is just trying to make such impression? To get the answer on this question, investigators will have to calculate all the unknowns of this complicated equation, that consists of crimes, mistakes and lies.