The ISS is not responding. After the corpse of Kurz, an ISS astronaut, is found in Kazakhstan, Baikonur summons French astronaut Anna Zarathi, wondering why Kurz yelled Anna's name before radio silence.

When he succeeds in formally identifying one of the previous corpses, Isaak wonders if he is not pursuing a killer of cosmonauts. Determined to save the crew of the ISS, Anna hopes to realise her dream of going into space.

Anna and Isaak are on the run, with Belinski, the head of security, on their heels and convinced that Isaak has engineered everything. In Baikonur, Fef is convinced that his sister, Irina, is hiding something about her husband and protecting him.

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

The ISS responds: the crew are alive and well. Durkov confirms the rescue mission and Anna prepares for the big departure. Fef and Isaak find the traces of the cosmonaut killer. Lydia sifts through MIR's archives and ends up finding the anomaly.

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