Elisabeth makes her way through the forest alone stopping near a crashed helicopter. She uncovers a hidden box containing a Doppler family photo, her old fox hat, and polaroids of Noah, a woman and their baby, Charlotte. Noah, in a voice-over, says the beginning is the end and the end is the beginning. Everything is interconnected. He couldn't tell Charlotte who her mother was.
The older and younger Noah stand next to each other at the Sic Mundus lair. The older Noah says there are things he was not able to share, even with his younger self. He would not exist if the younger had not followed in the same path that he did. They are not free in what they do because their will isn't free. Old Magnus and the woman enter, and say everything is ready. The older Noah tells the younger Noah to leave.
The younger Jonas and Claudia are in the Winden Caves. His future self had tried to close the wormhole to reverse it all but had not broken the cycle. The elder Claudia had told him that they could change one factor in the equation so that he would be successful on the next attempt, and all the subsequent events- Mikkel vanishing, their fathers dying- would never take place. All he would need to do is change the details- a grain of sand.
At the Tiedemann home, Bartosz asks his mother about his grandmother. He tells her that she had come to visit the previous Fall. Regina is startled to hear this. Bartosz hands her a photo of Claudia and Regina from 1986 and tells her that Claudia 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 and promises to return without answering Regina when she asks where he's going.
Clausen hands Aleksander a search warrant for the Winden Nuclear Power Plant. He vows that even if he cannot prove that Aleksander murdered his brother, he will still get him for whatever is happening in Winden. Aleksander, distraught, begs Torben to help him and stop Clausen. Torben says it is impossible and perhaps things will be better now the truth is out.
The Stranger, adult Jonas, goes to Martha's house. He tells her she must come with him and that it is his fault that everyone will die in a few hours when the new cycle begins and the future starts. Martha is confused by this but he begs her to trust him. He starts to caress her but she shoves him away, repulsed, saying they’re wrong together and tells him to leave. He refuses and grabs her arm and tells her he will not see her die again. He points the gun at her and tells her he is making things right.
With six hours left to the apocalypse, Bartosz meets Franziska and Magnus at the railroad bridge. He 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 and tell him what to do. 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.
Katharina arrives with the device at the Kahnwald house seeking Jonas but finds it empty. She looks around his room and finds his backpack containing the orb light and his annotated Winden Cave map.
The younger Jonas leads Claudia deeper into the cave to open the portal again, telling her he has accepted that he has to be part of the very disaster he wanted to prevent, having learned much from the older Claudia. There are two sides at war: Adam and Sic Mundus, who want to create a new world, and Claudia and himself, who want to save this one. Claudia does not know who Adam is.
The Stranger, adult Jonas, takes Martha at gunpoint to the bunker, which he tells her is the only safe place. She asks if he meant that Mikkel would return is true. He tells her Jonas will come back and everything will happen as it always has, but tells her to promise to remain there. He locks her inside and apologizes.
Jonas inserts a vial of radioactive waste in the cave into the machine, which activates it. "This is time", he says, "We connect past and future".
Charlotte returns to the police station and Torben, surprised to see her, warns her that Clausen has arrested Aleksander and obtained a search warrant for the power plant. Torben admits that he helped Aleksander hide a secret stash of radioactive waste on the grounds of the plant. Charlotte realizes that the waste is what triggers the apocalypse, as Jonas had told her.
Peter Doppler, at home, leaves a desperate voicemail for Charlotte, asking if Franziska is with her. He tells Elisabeth that they must leave because Noah has said only the people in the bunker will survive. Elisabeth asks about her mother and sister, Peter says that things will be okay. Clausen arrives at the plant. He is told he cannot go further due to the radiation, but Clausen insists.
Katharina comes downstairs and spies a photo album of Michael. Leafing through it she sees pictures of her son as he grew up which brings her to tears. The adult Jonas walks in. She asks him how to use the machine and bring Mikkel back. Jonas tries to explain that it's impossible. Katharina says that he doesn't want him to come back as he won't exist. Mikkel belongs there, he doesn't. He replies that the past can't be changed, as he already exists and that the events that lead to his existence cannot be changed. He says he would trade his own life for Mikkel's but can't because his future already exists. He thought he could prevent it but it's beyond his control.
Noah approaches Adam, accusing him of lying to him—that he never had an interest in saving anyone. Adam says simply that no one can escape his fate. Noah presents the missing pages from Claudia's notebook and throws them at Adam, saying Adam is not waging war on God, but on humanity. Angry at being used as a pawn, he pulls out a gun and aims it at Adam. Adam is unmoved, and says Claudia was right: Noah still does not understand. Noah pulls the trigger, but the gun does not fire. Time plays a game with us. It is not Noah's destiny to kill Adam, nor his to die now. We are only free when we are free of all emotion, only when one is ready to sacrifice what one holds dearest. He shows him a photo of Elisabeth. He tells Noah that Charlotte is his daughter, and that Charlotte is both Elisabeth's daughter and mother. "No human is without guilt," he says, "This knot can only be undone by destroying it entirely, We cannot escape our fate." Agnes then enters, takes the gun and shoots Noah. Following his death, the younger Noah leaves. Adam enters the god particle.
The noise of the wormhole opening is heard, lights flicker all around town, and dead birds fall out of the sky as Peter and Elisabeth drive to the bunker. They are surprised to see Martha there. Martha then rushes out before Peter can stop her.
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.
Teenage Jonas and Claudia (1987) exit the cave in 2020, the day of the Apocalypse. He tells her to take the machine to the bunker near Helge's cabin and heads off, saying he must find Hannah and Martha.
Alone at home, Regina is on the phone with the police, pleading for Aleksander's release, or to be able to visit him, but gets nowhere. Suddenly, 1987 Claudia appears at the door, telling her not to be afraid, quite unsuccessfully. Claudia apologizes for how she left, and asks Regina to come with her now. Regina bursts into tears as Claudia embraces her.
The younger Noah enters the Kahnwald home, where the adult Jonas is waiting—with the gun. Noah says Jonas looks different from when he saw him last, and that he wondered when Jonas became Adam. Jonas denies that he will ever do what Adam says, but Noah says Adam said they will become friends, before Jonas betrays him. Noah says he follows Adam, and Jonas follows Claudia, because they each hope for their own kind of salvation. Jonas raises the gun to Noah's chest, but Noah calmly pushes it back down, saying Adam/Jonas is the savior. Noah then hands him a letter—from Martha. Jonas reads it anxiously, saying it is impossible. Noah tells him that he must hurry to save Bartosz, Magnus and Franziska—and later him and Agnes. The loop must be closed so that the next cycle can begin, as prophesied, so that Martha can live. Jonas is beyond belief, however. He grabs the machine and hurries out.
Katharina goes to the caves with the map and orb light, and heads in. She follows the stream of time particles to the Sic Mundus door; as she opens it. Claudia and Regina go to the bunker to join Peter and Elisabeth. Peter realizes Claudia is the white devil from the picture there. Claudia stares at it strangely. They are later joined by young Noah.
The yellow drums of waste are dug up, as Charlotte and Torben arrive. Teenage Jonas returns to the Kahnwald house, calling for his mother, but it is Martha who responds. He has come back, just as Bartosz had predicted. She tells him she knows about everything, and understands what he said in the rain, and that it was him who visited her at the lake. She touches his face tenderly, and repeats what he said, that they are a perfect match, and not to believe anything else, and they kiss passionately and joyfully.
The moment is interrupted by Adam, who says that all the pieces are now in place, and just need a push. Jonas lashes out, saying he keeps lying, he wanted it the same way and he is the trigger for the cycle to repeat itself. Why does he want the awful future repeated? Adam says what is created will be the beginning of the end, that the dark matter must be created so that he can lead it to new purpose in the future, and bring about the end of the world. He draws a gun and says he is the trigger of what will make Jonas what he is today, and then shoots Martha in the chest. She collapses on the ground as a distraught Jonas tries to reassure her. Adam says coldly that some pain is unforgettable, that Jonas will carry it with him the rest of his life, until he is ready to let go of her. He circles June 27 on the wall calendar as Jonas sobs. Adam says Jonas can try to save her, or try to stop him, and that he will know what he has to do. He tells Martha not to leave.
Charlotte tells Clausen to stop, that opening the drums is a mistake. She says this is not about the missing people, but about the past, the future, and all their interconnections. Clausen brushes her aside and orders the drum be opened. In it are rocks covered in an oily black substance which coalesces into a throbbing mass from which a god particle forms.
The adult Stranger/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.
Meanwhile, in 2053, Elisabeth activates the generators in the God particle lab, and a wormhole opens up in the power plant, showing Elisabeth on the other side. Elisabeth and Charlotte walk towards each other from their respective times, Elisabeth signing Mom. As they greet each other, a massive time portal opens above the entire plant. As Elisabeth and Charlotte touch each other, the sky goes dark. Adult Jonas activates the apparatus, which envelops the teens, and they disappear.
Teenage Jonas, sitting over Martha's lifeless body, promises he will make things right. He is startled as another Martha approaches him. She says she is not who he thinks she is, she says she will explain later but he has to come with her. She activates an orb. He asks her what time she is from. "The question isn't what time, but what world", as the house is shattered by the shock wave of the arrival of the apocalypse.
- Noah: We're not free in what we do, because we're not free in what we desire.
- Jonas: Big and small things don't abide by the same laws. Maybe nothing big can be altered, but small things can. We're changing a grain of sand. And with it, the whole world.
- Martha: Let me go!
Jonas: I can't. I promised you I'd make it right. I'm making it right.
- Bartosz: Why didn't Noah tell me what to do? Why did he tell me it all? Explains the thing to me and doesn't tell me what to do with it.
Franziska: Maybe you did exactly what you were supposed to do. You showed us how it works. Maybe that was your sole task.
- Claudia: What's that?
Jonas: The passage. We're opening it again.
Claudia: You said you wanted to shut it, in the future… or the past. Your future!
- Jonas: You taught me everything about the future and past. Everything that happened, everything that will happen. There are two sides out there. Adam and Sic Mundus want to create a new world. You and I want to save this one.
- Katharina: How can I bring Mikkel back?
Jonas: Even if I explain it to you, it's impossible.
Katharina: You don't want him to return. Because then you'd no longer exist.
Jonas: I wish it were so simple. Things in the past can't be changed. Mikkel can't return because I already exist.
Katharina: Mikkel belongs here, and not you! You shouldn't exist at all.
Jonas: Yes. I'd trade my life for his anytime. But I can't die, because my future already exists. You'd be just as incapable of bringing Mikkel back.
Katharina: Then why did you return?
Jonas: I tried to prevent the origin. But it's impossible; I can't. Adam is the endpoint. Maybe I can't prevent myself from becoming what he is, but I can stop what has become of me.
- Adam: Only when we're free of all emotion are we truly free. Only when one is ready to sacrifice what one holds dearest. Charlotte is your daughter. She is Elisabeth's daughter. And her mother. No human is without guilt. None of them have earned a place in your paradise.
- The young Noah says the older Jonas looks different from when he saw him last, a callback to "The Travelers," in which he says the younger Jonas looks different from what he expected.
- Martha tells the teenage Jonas "We're a perfect match, don't ever believe anything else," repeating what he told her at the lake, but contradicting what she said to the adult Jonas that they were "wrong."
- Clausen in uncovering the dark matter in the power plant connects Charlotte in 2020 with Elisabeth in 2053 (similar to when Jonas and Helge were connected in season 1).
- What is in the letter from Martha? When did she write it, and how did Noah come into possession of it?
- Did Katharina travel to another time and find Ulrich and/or Mikkel?
- Does older Jonas take Bartosz, Magnus and Fransiszka to another timeline?
- What world is the alternate Martha from?
- Bootstrap paradox: Charlotte Doppler is Elisabeth Doppler's mother but is also her daughter! Elisabeth and young Noah were together in the bunker. Noah, in a voice-over, says the beginning is the end and the end is the beginning. He couldn't tell Charlotte who her mother was: Elisabeth. They also meet in season 1 when Elisabeth was a girl and gives her the watch with Charlotte engraved.
- The English subtitles for this episode include at least one typo; at 35:33 they say "Buy" instead of "But".
- The Kahnwald house is blown up in the apocalypse in 2020 but is still standing when Jonas travels to 2052 (Beginnings and Endings).
- Sandra Borgmann as Elisabeth Doppler (2053)
- Karoline Eichhorn as Charlotte Doppler
- Carlotta von Falkenhayn as Elisabeth Doppler
- Stephan Kampwirth as Peter Doppler
- Mark Waschke as Noah
- Max Schimmelpfennig Noah (1921)
- Wolfram Koch as Unknown Man in 1921
- Carina Wiese as Unknown Woman in 1921
- Andreas Pietschmann as The Stranger
- Louis Hofmann as Jonas Kahnwald
- Julika Jenkins as Claudia Tiedemann (1987)
- Paul Lux as Bartosz Tiedemann
- Peter Benedict as Aleksander Tiedemann
- Sylvester Groth as Investigator Clausen
- Lisa Vicari as Martha Nielsen
- Moritz Jahn as Magnus Nielsen
- Gina Stiebitz as Franziska Doppler
- Jördis Triebel as Katharina Nielsen
- Dietrich Hollinderbaumer as Adam
- Antje Traue as Agnes Nielsen (1954)
- Leopold Hornung as Torben Wöller