Isaak discovers the events that took place aboard the MIR station 25 years earlier and unlocks the secret of the killer's identity. In the damaged station, covered in frost and soon deprived of oxygen, Anna finds part of the crew and tries to bring everyone back to Earth.

After his latest discoveries, Isaak wonders if he is not pursuing a killer of cosmonauts. Determined to save the crew of the ISS, Anna begins to dream that she will go into space. At the cosmodrome, Emil Durkhov and the other engineers are looking for a way to communicate with the space station.

The ISS, the International Space Station has gone silent. The crew is in distress. Simultaneously, a decapitated and waxed body is found on a roof in Kazakhstan. Positive identification leaves no room for doubt: the body belongs to an American astronaut currently on a mission on the ISS. A French astronaut, dismissed from the space program, and a Kazakh cop, disowned by his ranking hierarchy, set out to solve this mysterious paradox.

Anna and Isaak are on the run with, hot on their heels, Belinski, the head of security. In Baikonur, Fef is convinced that his sister Irina is hiding something about her husband. At the cosmodrome, Mikhaïl and Réva suspect a hack at the origin of the accident. Anna joins the tracking station where Gilgamesh lives.

Lydia and Réva understand that the American satellite has been hacked from the cosmodrome. Their investigation leads them to the MIR archives. Questioned by Belinksi, Gilgamesh refuses to speak. In the middle of the irradiated zone, Anna and Isaak manage to reach the landing point of the Soyuz.

The International Space Station finally responds: the crew is alive and well. Relieved, Durkov confirms the rescue mission, so Anna prepares for the big departure. Fef and Isaak find the traces of the cosmonaut killer. For her part, Lydia goes through the archives of MIR and ends up finding the anomaly that could explain everything.