As "Madame Ostrakova" (Eileen Atkins) is confronted by a man while attempting to get on a bus, it’s revealed she has a hidden history connected to the Soviet Union, which led her to leave her daughter behind in Moscow. Confronted with a tough decision, she reaches out to a man who might be able to assist her. That man is "Gen. Vladimir" (Curd Jürgens), and he happens to have connections to the now-retired "Smiley" (Sir Alec Guinness), who’s pulled from his quiet life to unravel a puzzle involving his own wife, "Lady Ann" (Siân Phillips), his longtime enemy "Karla," this woman, and her abandoned daughter. John Le Carré was involved in adapting his own story for the screen, and Sir Alec Guinness brings a very deliberate touch to shaping his portrayal of this thoughtful and clever spy-master. However, unlike "Tinker Tailor...", it doesn't quite have that feeling of being mysterious. To be straightforward, it’s fairly obvious who everyone is, and the connections in the story are much easier for viewers to figure out. The supporting actors do a good job, with notable performances from Beryl Reid and the consistently dependable Michael Lonsdale; Jürgens lends weight to his role, while Michael Byrne (the new "Guillam") and Anthony Bate’s “Lacon” also contribute positively as the story explores how the Soviet system of control dangerously influenced its agents abroad. The pacing is good if you prefer your drama more intellectual, with limited dialogue and chances for the audience to participate in solving the mystery themselves. It isn't quite as strong a sequel—mainly because the storyline itself isn’t as compelling—but it remains an engaging six-episode series that lets some of Britain’s finest character actors showcase their talents alongside a script that skillfully presents the puzzle within the plot.

Source on TMDB