Moscow, at the beginning of the eighties, in the middle of the Cold War.
Sergey Grigoriev, a KGB colonel disappointed with his country's regime, decides to bring down the system. He makes contact with Pierre Froment, a young French engineer posted to Moscow. The highly confidential information Grigoriev passes to Froment quickly attracts the attention of the Western secret services.
President Mitterand is alerted and decides to inform President Reagan: a huge spy network allows the Soviets to know everything about the scientific, industrial and military research being carried out in the West. The two heads of state decide to exploit this ultra-sensitive data transmitted by a mysterious Moscow source whom the French have baptized "Farewell."
A simple man, Pierre Froment hence finds himself embroiled in one of the most astounding spy cases of the 20th century. A case that is way out of his league and that soon threatens his life and the lives of his family.