Sometimes, treachery is nothing but instinct. An outdoor officers information stirs the precious calm gained hardly by British Intelligence agency the Ground (refers to MI6/CIA). There is a double side spy who was inserted at the Ground by Soviet Intelligence chief Carla, and the spy is one of the top four in Ground. Under the mess, Smiley, who has been forced to retire, is asked to prosecute an inquiry. Who is the real one in the back of the plot, Tinker, Tailor, Soldier or Spy? Smiley, whose memory is as good as a computer, enters into a pile of data to search for clues. Finally, he solves the last smart plot set by Carla.