In John le Carré's Tinker Tailor Soldier Spy , Ricki Tarr’s investigation into a Soviet mole named "Gerald" serves as the catalyst for George Smiley to return to service. After his informant, Irina, reveals a high-level traitor within the British Circus, Tarr goes into hiding following a betrayal, eventually detailing the story to Smiley. You can explore the narrative, including the 1979 TV series, in detail at IMDb .