Tinker Tailor Soldier Spy (2011) on Netflix

A year after he was forced into retirement, ex-spy George Smiley is called back by a Cabinet office official when information comes to him that there may be a Soviet spy, a mole, at the very top of the British secret service. Smiley had been forced out along with Control, the head of spy agency, after a disastrous mission in Hungary where a colleague, Jim Prideaux, was shot. It was also an unhealthy time in the secret service, known affectionately by its members as the Circus, with several senior officers having developed a new source of information in the USSR but refusing to share that person's identity. Smiley agrees to return and in the course of his examination learns that the secret secret Soviet source has become the mainstay of the service, one that they soon plan to use to get at US intelligence information. Smiley soon realizes that the Soviets have turned the service inside out.