This French movie is a fictionalized account of an historic Cold War spy operation invoving a KGB colonel who supplied France and, by extension, the US, with critical information. Although the movie was in french with subtitles, there were some American actors, such as Willem Defoe and David Soul.
The KGB colonel in the movie is named Sergei Grigoriev, but the real world KGB colonel was named Vladimir Vetrov. The French gave him the english codename of Farewell. Vetrov, an engineer, worked in the departmnent that handled technical/industrial intelligence. Because the communist system did not encourage innovation, they relied very heavily on technology stolen from the West, for both civil and military uses. The information provided by Vetrov told the US just how vulnerable the Soviets were. The US's resulting strategy was to exploit that weakness through denial (rounding up the agents whose names were provided by Vetrov) and deception (such as providing the Soviets with plans that were either unworkable or unsafe).
Although the story is rarely known, even though it's about a critical phase of the Cold War, I wasn't that impressed with the movie. The story seemed to be poorly told and somewhat disjointed. Perhaps there was just too much material to cover in two hours. The movie covered not only the personal lives of the KGB spy and his Fench contact, but also the US strategy and the Soviet's response.
I would say that it was decent, but not excellent. A viewer who likes true life espionage –– as opposed to James Bond action –– would like it. But I don't think that it's nearly as good as "Tinker, Tailor, Soldier, Spy" (the old Alec Guiness version) or "The Company." I note that both of those were miniseries, not feature length movies.