Kasia Tomaszeski

 is a young Polish women who joins the Polish resistance. The war causes her family to be torn apart with her parents being murdered, husband fighting in France, one brother on the run across Europe and another in England. Kasia's story is one of survival and danger as she vows to save her country and humanity but in doing so loses everything. The physical and emotional impacts soon begin to build up and Kasia has no other option but to keep on fighting until her time runs out.

Biography
 Season 1, episode 1 

Kasia was born to Stefan and Maria Tomaszeski and sister to Grzegorz and Jan. Prior to the bombing of Poland, Kasia worked as a waitress in one of Warsaw's cafés in a love affair with the young English translator Harry Chase, unaware that he already has a girlfriend at home. Her father and Grzegorz departed for Danzig to defend against the imminent German invasion, leaving Kasia with her mother and Jan at home in the city. Her father is killed in Danzig but her brother manages to escape. While Warsaw is being bombed by the Germans, Harry proposes to Kasia so she can leave with him as his wife and go to England. She accepts and they get married. However she feels that she cannot leave behind her brother and unstable mother, instead of her getting on the train out of Poland with Harry, she puts her brother on it in her place and stays behind to look after her mother.

 Season 1 episode 2 

As the Nazis are getting closer and closer to Warsaw, Kasia makes plans for her and her mother, Maria to flee Poland. Kaisa is suddenly caught in a resistance attack on the Germans, her and a resistance fighter Tomasz race to Kasia's home just as the German soldiers break in. Maria argues with one of the soldiers and spits at him, he then shoots her in the head and she dies in Kasia's arms. Later as German Soldiers are rounding up Poles, Kasia sees Grzegorz, she tells him to get out of Poland but doesn't tell him that their mother is dead. Grzegorz and his friend leave Kasia a gun which she later is about to use on a German solider tormenting a Jewish person until Tomasz stops her. She convinces him to let her join the resistance and she vows to save her country even at the cost of her own life.

 Season 1 episode 3 

Kasia is now part of the resistance, she is told to pick out a German and lead him down an alley way where Tomasz will kill him. She agrees and lures Klaus down the bombed alleyways but lets him go after he starts talking to her about his family. Later she manages to control her nerves as she leads a German soldier away, she kisses him as Tomasz pulls out a gun, Kasia walks away as Tomasz shoots him.

 Season 1 episode 4 

Kasia and Tomasz pick out their next target, she brings him down an alleyway and kisses him but Tomasz doesn't appear. As the soldier tries to force himself onto Kasia, she is forced to shoot him herself, Kasia is clearly traumatised by what she has just done. Later Kasia witnesses the SS rounding up 30 poles and shooting them, she then vows to kill as many Germans as the firing squad did.

 Season 1 episode 5 

For Kasia killing becomes normal and she has completely changed from who she used to be. Her and Tomasz fear that they have somewhat turned into the people they are fighting against. In fighting for humanity Kasia has lost her own, she explains that even though she remembers everything about the first man she killed and how it haunts her, she has now become numb and doesn't feel from that moment onwards.

 Season 1 episode 6 

Kasia misses Harry and her family, fearing she will never see them again. She looks at a photograph of her, Harry, her parents and Brothers and breaks down.

 Season 1 episode 7 

Kasia and Tomasz are caught trying to kill a German, Kasia is taken to a cell where she sees Tomasz has been hung and is wearing a sign around him that says Jew and traitor. The next day Kasia is taken out to be executed, she has excepted her fate and is not fighting it. However just as she is about to be hung a bomb is set off by the resistance and Kasia is led away by 2 resistance fighters. Kasia ends up at a barn where some resistance fighters are, surprisingly one of them is Harry on an SOE mission to get them out of Poland. She tells Harry that she is no longer the girl he fell in love with and doesn't deserve to be happy with him after everything she has done. Harry manages to convince her to come with him. A truck arrives, which they believe is their way out of Poland, however Germans emerge from the truck and begin shooting at them. Harry and Kasia are the only ones who make it out of the barn, they then split up to avoid being shot at and Harry tells Kasia to meet him at the top of the hill. The series ends with Kasia looking up at Harry -who is at the top of the hill- from the forest with the Germans close behind.