She faces domestic pressure from Georgy’s mother, who is actively trying to force her to leave their shared apartment and divorce her husband.

Just as Petr Natanovich joins the investigation, Volynin's body disappears from the morgue. While this causes panic for Korzun, Katerina views it as proof that the death was a calculated murder rather than an accident.

The tension peaks when Shefner catches Sonya searching through his personal belongings. Character Arcs in Season 4

The season follows the series' established structure, where every four episodes typically cover one major criminal case. Шифр (телесериал) - Википедия

The episode revolves around the mysterious disappearance of a body and the meticulous gathering of evidence by the former GRU codebreakers.

Continues to balance her analytical work with complex family dynamics, often leading the group's tactical efforts. Production Details

She struggles with a secret pregnancy by Letnev, which she hides from her peers.