He soon focuses on the details of the Circus 's best source of intelligence on the Soviet Union , codenamed Merlin .
Smiley accepts Lacon 's request to begin his investigation in absolute secrecy .
Smiley soon focuses on the details of the Circus 's best source of intelligence on the Soviet Union , codenamed Merlin .
Smiley accepts Lacon 's request to begin his investigation in absolute secrecy .