Tinker, Tailor, Soldier, Spy
John le Carré
 Through a love affair in Hong Kong with Irina, the wife of a Moscow Centre intelligence officer, British agent Ricki Tarr discovers that there may be a high-ranking Soviet mole, codenamed "Gerald," within the Circus. After going undercover to avoid Soviet agents, Tarr alerts his immediate superior, Peter Guillam, who in turn notifies Undersecretary Oliver Lacon, the Civil Service officer responsible for the Intelligence Services. Lacon enlists George Smiley, the retired former Deputy Head of the Service, to investigate. Smiley and Guillam must investigate without the knowledge of the Circus, which is headed by Sir Percy Alleline and his deputies Bill Haydon, Roy Bland, and Toby Esterhase, as any of these could be the mole. Smiley suspects that Gerald was responsible for the failure of Operation Testify, a mission in Communist Czechoslovakia, the ostensible purpose of which was to meet with a defecting Czech Army general. Operation Testify ended with Circus agent Jim Prideaux shot in the back and tortured, and caused the disgrace and dismissal of Control, head of Circus, who subsequently dies. Prideaux, who survived and was repatriated and dismissed from the Circus, reveals to Smiley that Control suspected the mole's existence, and the true aim of Operation Testify was to discover the mole's identity. Prideaux reveals that the Moscow Centre personnel who interrogated him already knew this, and it became clear to Smiley that the operation was a trap set by Moscow Centre to discredit Control and remove the threat to their mole Gerald. Percy Alleline, who was Control's rival, has risen to head the Circus as a result of seemingly top-grade Soviet intelligence from a source code-named "Merlin." The Merlin material is handled by a secret committee, consisting of Alleline, Haydon, Bland, and Esterhase, in an operation called Witchcraft. Smiley's investigation leads him to believe that the Merlin source is false, and is being used by Moscow Centre to influence the leadership of the Circus. Cleverly, Moscow Centre has induced the Circus leadership to believe that Merlin maintains his cover in Moscow by feeding the Russians low-grade British intelligence, "chicken feed", from a false Circus mole. As a result, the leaders of the Circus suppress any rumours of a mole, protecting the actual mole. Smiley contrives a trap for the mole, using a communication from Tarr, and Gerald is revealed to be Bill Haydon, a respected colleague and former friend who once had an affair with Smiley's now estranged wife, Ann. Haydon is arrested, and acknowledges he was recruited by Karla, the Moscow Centre spymaster. Percy Alleline is removed, and Smiley is appointed temporary head of Circus to deal with the fallout. Haydon is to be exchanged to the Soviet Union for several of the agents he betrayed, but is mysteriously killed while in custody, shortly before he was due to leave England. Though his killer is not explicitly revealed, it is strongly implied to be Prideaux, his old partner, whom he betrayed in Operation Testify.