The Jigsaw Man (1983)

Philip Kimberly's a former head of British secret service, who had defected to the Soviet Union. One day, he receives instructions; he's to go back surreptitiously to the West, with the goal of retrieving some important documents. After having plastic surgery to alter his appearance, he is put back on the western side. When he accomplishes his goal, he thinks his handlers won't need him anymore. So, with the documents in his possession, rather than returning to the East, and possible assassination, he instead plays one side off against the other--KGB against Mi6.