1x22 - Snowdrop

Irina reads a letter sent by Nadya in which Nadya makes it clear that she is aware of Irina being Rita's real murderer. Nadya assures Irina that she will prove her crime and get her behind the bars. Irina is shocked reading the letter and begins crying out of guilt. However, Irina collects herself together and believes that Nadya cannot prove anything against her.