Tinker Tailor - S1.E5

Smiley, now fortified with new information, goes to confront Jim Prideaux, an old spy who long since came in from the cold and is now a school teacher. Control, in his last days, seemed to have confided in him and sent him on a mission behind the Iron Curtain to find out who exactly the mole in the Circus was, Tinker, Tailor, Soldier, Rich man, or Poor man.