It is spring in 1963 and George Smiley has left the Circus. With the wreckage of the West's spy war with the Soviets strewn across Europe, he has eyes only on a more peaceful life. And indeed, with his marriage more secure than ever, there is a rumour in Whitehall – unconfirmed and a little scandalous – that George Smiley might almost be happy. But Control has other plans. A Russian agent has defected in the most unusual of circumstances, and the man he was sent to kill in London is nowhere to be found. Smiley reluctantly agrees to one last simple task: interview Susanna, a Hungarian émigré and employee of the missing man, and sniff out a lead. But in his absence the shadows of Moscow have lengthened. Smiley will soon find himself entangled in a perilous mystery that will define the battles to come, and strike at the heart of his greatest enemy…