 When contacted by Tarr and unsure of whom to trust, he goes to senior Civil Servant Oliver Lacon and, acting as his link man, Guillam facilitates Smiley's secret return from retirement in order to conduct a surreptitious investigation into the identity of the mole.Guillam is motivated not only by his loyalty to Smiley but also because, as a result of Gerald's actions, a network of secret agents he ran in Former French North Africa were identified and executed.Guillam acts as Smiley's man on the inside in the investigation, which involves his actually stealing files from The Circus Registry at Smiley's request.