In February 1965, a Soviet project involving an orbital bomb threatens the geopolitical balance of the world. The French secret service hires Francis Mareuil, an aerospace engineer, to recruit Boris Golubev, the scientist whose research made this bomb possible. In Moscow, the KGB puts Boris under surveillance by forcing his daughter Lyudmila to spy on him.

In East Berlin, Francis finds out that Boris is under constant surveillance by the Stasi, the East German intelligence agency. He bonds with Lyudmila, convinced that she can get him access to her father, but oblivious to her ties with the KGB.

Boris Golubev heads the launch of a space probe that turns into a fiasco -- the probe lands in the Algerian desert. When he contradicts the Soviet army about how to handle the crisis, they place him under house arrest. Meanwhile, Francis tries to find a way to save Lyudmila by bringing her West, even if it means risking it all.

Lyudmila is back in Czechoslovakia with her wounded father and is in danger -- the KGB is tracking her down. Francis tries to understand what Boris found in the probe and retreats further and further away from his family.

Lyudmila is alone and stuck in Czechoslovakia. Francis reconciles with his wife and takes part in a mission co-led by the SDECE and the CIA with a common goal of contacting Boris.

While investigating Charles Contignet, Anne makes a troubling discovery. She decides to tell her husband about it. Hunted by the KGB, Lyudmila hides with a Czech family. There's only one way out for her -- contacting Francis and asking him to come save her.

In Czechoslovakia, Francis jumps through hoops to find Lyudmila. As they try to get back West, Yemelin and his henchmen chase them down. Anne finds a top-secret document and is now in danger. She must flee.

As the orbital bomb is about to crash, Francis, Lyudmila and Anne risk capture and death. Yemelin, through powerful allies in France, will do anything to get the numbers back, as well as the list.