After a routine security check by George Smiley, civil servant Samuel Fennan apparently kills himself. When Smiley finds Circus head Maston is trying to blame him for the man's death, he begins his own investigation, meeting with Fennan's widow to find out what could have led him to such desperation...

After a routine security check by George Smiley, civil servant Samuel Fennan apparently kills himself. When Smiley finds Circus head Maston is trying to blame him for the man's death, he begins his own investigation, meeting with Fennan's widow to find out what could have led him to such desperation.