In 2019, his mother Regina owns and operates the Waldhotel Winden, and his father Aleksander is the director of the Winden Nuclear Power Plant. This places Bartosz among the wealthy elite in a town of mostly blue-collar power plant employees, but also isolates him from his classmates. Jonas is his only friend, and when Jonas is not around Bartosz spends his time alone smoking pot and playing video games. He seeks ways to prove himself and to fit in.
When Jonas was in treatment after his father Michael's suicide, Bartosz told their classmates he was on an exchange program in France, trying to protect him. At the same time, he became romantically involved with Martha Nielsen, who had been Jonas' girlfriend over the summer.
After the disappearance of Erik Obendorf, Bartosz leads Jonas and the Nielsen siblings into the woods near the Winden Caves in the hopes of finding Erik's stash of drugs. When they arrive, Franziska Doppler has already 'claimed it'. Bartosz takes it from her forcefully by pushing her to the ground. The group is frightened by loud roaring coming from the cave and scatters. A few days later, he receives a call from Noah, and thinking him to be Erik's supplier, plans to meet him with Jonas later. Bartosz goes alone, however, when Jonas never shows up.
On the afternoon of November 11, Bartosz is surprised to meet his grandmother, Claudia Tiedemann, whom he had thought was dead. He meets with Noah that night and, as events have transpired as predicted since their first meeting, agrees to do as he says. The following night, he meets with Noah again and the priest explains the nature of their war. Bartosz learns from Noah that his grandmother Claudia is of the shadow and that she is their primary enemy, that Jonas Kahnwald is merely her puppet in this war, and that they belong to the light although some of what they do may be dark. Noah then gives Bartosz his triquetra notebook.
Bartosz looks on as his mother, who is now pale and having lost hair as a result of her cancer treatment is visited by her doctor. He tells her he is worried about her lab results and suggests she be admitted to the hospital, but she insists on staying at home. The doctor agrees to wait until additional test results come in, but warns that she may need to resume chemotherapy.
June 24 Edit
When Franziska, Elisabeth, Martha and Magnus go to the caves they hear footsteps. It is Bartosz, carrying a suitcase. They demand to know what he is doing there. Magnus punches him. They open his suitcase and ask him what it is. He tells them it doesn't concern them. Magnus tells Bartosz that if he has anything to do with the disappearance of his brother and father he will kill him. Martha tells Bartosz they will leave him there overnight, and take the suitcase.
June 25 Edit
The teenagers return to the Winden Caves and are observed by Noah. Bartosz is still tied up there. They ask him what is going on. He says he cannot tell them and even if he did, they wouldn't believe him. Franziska tells him that the human body can survive three days without nourishment, and they all prepare to leave. Finally, he tells them it is a time machine. Magnus does not believe it, but Martha tells Bartosz to show them how it works. Bartosz says he needs a phone. Martha hands him hers. This activates the device.
The teenagers emerge from the cave and realize the landscape is different, the chair is missing. Bartosz says he didn't believe it at first either, but Noah told him what would happen before they happened: Martha would kiss Jonas, his mother would get cancer, Jonas would disappear but he will soon return. Franziska says Elisabeth knows Noah. Magnus scoffs and leaves, the others following. Bartosz asks Martha if she trusts him. She does not answer and goes to join the others.
They emerge from the forest and come to the bus stop. Posters advertise a 1987 concert. Police cars drive past, containing Ulrich, who recognizes his children and tells the police to stop but they drive on. Bartosz asks them if they believe him now. Martha looks at him and walks off with the others.
June 27 Edit
Bartosz asks his mother about his grandmother, telling her that she had come to visit the previous fall. Regina is startled to hear of this. Bartosz hands her a photo of Claudia and Regina from 1986, and tells her that Claudia had said she was sorry—and if she could turn back time, she would have done things differently. Regina is moved to tears,. Bartosz kisses her tenderly, then excuses himself, promising to return, without answering when she asks where he is going.
With six hours left to the apocalypse, Bartosz meets Franziska and Magnus at the railroad bridge, and demands to know where the time machine is. Magnus says Katharina has taken it. This disturbs Bartosz, who is angry that Noah did not explain things to him, but Franziska says that perhaps showing them how the device worked was his only job. Bartosz runs off to try to find the machine, and the others follow.
Magnus, Franziska, and Bartosz are at the Nielsen home looking for Martha and Katharina, but cannot find them. Bartosz says that Noah was right, and Jonas is to blame for everything. The adult Jonas goes to the Nielsen home and pounds on the door. Bartosz recognizes him when he enters, saying it is all Jonas' fault, which Jonas freely acknowledges. He says he has come to save them from the apocalypse, but has no answer when they ask about Martha. They all time travel at the last second.
1888 (time travel) Edit
September 22 Edit
Months after time traveling, Bartosz was stuck in 1888 with his group. One day, Martha walks out of the room she was in and sees Bartosz, Franziska, and Magnus who all look at her in disbelief. Magnus hugs her, but Jonas tells him that that is not Martha. Since they are all confused, Martha says that she is not the Martha they knew, and that she is trying to fix everything.
The group ask Martha to clarify what she was saying about being from a different world, and tells them that her world ends exactly like theirs. Magnus finds it ridiculous because he is not dead, but Jonas asks how they were found. Martha tells him that Jonas told her, but Franziska is quick to point out she had already said there was not a Jonas in her world. Martha explained that Jonas traveled from their world to hers, but older Jonas tells Martha that she is lying because he never went to her world. He gets aggressive and asks her what she really wants and if Adam sent her.
A door opens and tells the group that they need to start the machines, as they are running late. The man points out they have a visitor, while Jonas leaves.
At the Tannhaus machine factory, Martha gets visited by Bartosz, who says sorry for Jonas. He mentions that ever since they got there, he had changed. Martha asks how they had gotten there, and Bartosz says they traveled when everything came to happen, but Jonas did not want to go to 1888 - it was simply what had happened. And since they had no nuclear energy, they had no means of traveling back to another time. Martha asks about the workshop and the blind man, and when asking if he knew where they were from, Bartosz asks her to come with him to show her something.
Jonas walks into Martha's room only to find it empty, as she was with Bartosz, who led her to a door, which took them to a room identical to Adam's study. Martha asked Bartosz what this was, and he told her it was sort of a secret society of which old Tannhaus was the only one left. Tannhaus' father was convinced he could supersede the rules of time and space, and dedicated his life to doing that, which his son followed in doing. Bartosz tells Martha that what Jonas is trying now is to rebuild a time machine the way he saw them, and had been there already, but only in the future. After this, he reminds Martha that Jonas had asked her if Martha had sent her because Adam killed Martha. He asks Martha who Adam is, and Martha wonders why Jonas had not told him that Jonas himself is Adam.
September 23 Edit
At the Tannhaus Machinery Factory, Bartosz and Martha return as an angered Jonas approaches them and asks where they had been. Jonas asks what Martha had told him, and Bartosz simply replies that they had been stuck there for weeks, and Jonas had no idea how anything worked while knowing exactly what would happen, but keeping it secret from them. Jonas pleads with Bartosz to open his eyes and realize he was being used because that was not the real Martha. Jonas reminds everybody that Martha is dead, while Magnus looks down sadly, and tells Bartosz that nobody can come back from the dead.
Magnus looks at Franziska and tells Jonas that whoever she may be, she could be the only way they have to escape 1888. Bartosz asks Jonas why he had not told them the truth and orders him to tell everybody who really killed the Martha they knew. Jonas is not able to do it and leaves, so Bartosz rushes after him and pushes him to the ground and once again telling him to tell everybody who Adam is. Jonas gets up and pushes Bartosz back, starting a fight between the both of them until they are separated by Magnus and Franziska. Bartosz reminds everybody that he had told them that Jonas was always to blame for their problems and reveals to them all that Jonas is Adam before storming off.
Later, when Martha gave Jonas dark matter to time travel out of 1888, Bartosz es present when Jonas places the orb in a bowl, while the rest of the group watches. He starts a machine, which lets off electric energy. The energy strikes the orb forming a god particle, which ultimately does not stabilize. Looking inside the bowl, the group sees the orb is destroyed. Franziska asks where Martha is; she is in her room grabbing a lantern and her orb. She uses another sphere and places it in the orb. She turns the orb and places it on the ground and disappears as soon as Bartosz and the rest of the group enters the room.
2019 (alterate version) Edit
November 4 Edit
Bartosz walks up to Martha and Magnus at school. They give each other a handshake, and Martha asks if he had seen Kilian, to which he responds that he had not. Kilian shows up, and says hi to Martha, who kisses him. Bartosz asks about Erik, but Kilian says they have no news on him. They hear an announcement on the school's PA in which Katharina summons all students to an assembly in the gymnasium. Magnus points out that it could be relating to his brother, and Kilian replies that Erik had never left home for two weeks, and when things got complicated he would contact his family, but this time they had not received any messages. They head to the gymnasium.
Bartosz explains to his classroom how black holes form, but is interrupted when Jonas walks into the classroom. The professor asks who he is, and he introduces himself, but the professor is confused because he had not been informed of any new students. Jonas makes up an excuse and manages to sit behind Martha, as Bartosz continues with his explanation.
In the forest, the teenagers walk as Kilian asks Martha why Jonas acted as if he knew her. Martha says he did not, and thinks it is strange. Bartosz changes the subject by mentioning Nostradamus predicted that the world would end that year, and Magnus thinks that is ridiculous. Jonas walks to the Nielsen's, but finds no lights turned on. In the woods, Kilian is hoping to find Erik, saying the police could have missed something.
Magnus asks the group if they know the story of the cave monster, which he says is legit. However, as he was going to tell it, they heard noises all over the place, including inside the cave. Their flashlights start flickering, and they start running away from the cave. In the bunker, Bartosz asks if everything is over, to which Magnus replies that he thinks so. Inside the bunker, a wormhole opens and a kid falls, with his eyes completely destroyed. Opening his jacket, Martha finds a student card, which reveals the kid to be Mads Nielsen.