Tinker Tailor Soldier Spy

Description for TINKER TAILOR SOLDIER SPY by John LeCarre':

A modern masterpiece, TINKER, TAILOR, SOLDIER, SPY begins George Smiley's chess match of wills and wits with Karla, his Soviet equivalent, as he's assigned to identify and destroy the double agent--a mole--who has burrowed his way into the top echelons of British Intelligence Headquarters.

This is #5 in A George Smiley Novel.