 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.Over the course of the novel, Guillam grows progressively paranoid and anxious regarding the investigation, at one point doubting the veracity of Tarr's allegations.When the mole is finally identified, Guillam loses his temper and physically attacks him, having to be restrained by the other men in the room.