Season one is set in November of 1953, 1986 and 2019.
- Plans to erect the Winden Nuclear Power Plant. ("Secrets")
- Thursday 5th: Erik Obendorf appears dead in the bunker from 1986.
- Monday 9th: Yasin Friese appears dead in the bunker from 1986.
- Tuesday 10th:
- The bodies of Erik and Yasin are found buried in a pile of sand in the nuclear plant construction site.
- Agnes Nielsen arrives in Winden with her son Tronte.
- Ulrich arrives from 2019. He meets his grandmother Agnes and his father Tronte on the road, then visits H.G. Tannhaus.
- Helge makes Claudia Tiedemann's dog Gretchen run into the cave and she disappears.
- Ulrich tries to kill little Helge by hitting him with a rock so that he could prevent all the kids' murders in the future. He hides him in the bunker, but he survives.
- Friday 11th:
- Saturday 12th:
- Construction of the Winden Nuclear Power Plant is authorized after the Atomic Energy Act is passed. ("Secrets")
- Thursday 21st: Birth of Aleksander Köhler (real)
- Friday 21st: Birth of Mads Nielsen
- An explosion occurs in the Winden nuclear plant, which is the first step to the caves' time-travelling powers.
- Tuesday 4th:
- Wednesday 5th
- Friday 7th
- Saturday 8th: Young Jonas arrives from 2019.
- Sunday 9th
- Tuesday 11th
- Boris Niewald arrives in Winden, running away from something, with a gunshot wound on his chest and carrying a bag with a gun and a fake passport. He adopts the identity of Aleksander Köhler. He hides the bag, but it's found by Hannah.
- Hannah tells Katharina that Regina was the one who told the police about Ulrich raping her, in an attempt to protect herself.
- Ulrich is released from the police station.
- Claudia Tiedemann finds her dog Gretchen whom she lost in 1953 at the place where the radioactive barrels are hidden. She finds out about the incident.
- Old Helge spies on his past self at the cabin.
- Helge is not coming to see Egon for the interrogation, so he goes to his cabin in the woods. He hides and pretends there's nobody home.
- Aleksander tries to get a job at the nuclear plant.
- Wednesday 12th
- Older Jonas comes back to see Tannhaus and brings the substance to activate the artifact.
- Old Helge tries to warn his past self about Noah's lies, but he doesn't listen.
- Jonas goes to the hospital to bring Mikkel back to 2019, but is stopped by Noah and Helge.
- Jonas wakes up in the bunker and is visited by his future self, who reveals his true identity.
- In a last attempt to stop himself, old Helge crashes a car into his past self. He dies but younger Helge is just injured.
- Older Jonas activates the artifact inside the portal, trying to put an end to the 1953-1986-2019 cycle and close the portal forever. This opens a hole in the bunker and makes the whole town shake.
- Jonas watches the hole open and sees Helge from 1953 on the other side. They touch hands and he's suddenly transported to the future / an alternate reality.
- Peter Doppler arrives in Winden.
- Birth of Erik Obendorf
- Birth of Mikkel Nielsen
- Friday 21st: Michael Kahnwald hangs himself and leaves behind a letter that is not to be opened before November 4 at 10:13 PM. ("Secrets")
- Tuesday 22nd: Erik Obendorf goes missing.
- First day of school. Jonas Kahnwald returns after being in therapy for two months, finds out that Martha Nielsen and Bartosz Tiedemann are a couple. ("Secrets")
- Helge Doppler escapes from the rest home and interrupts a meeting at school to tell them "It's going to happen again." ("Secrets")
- Ines Kahnwald opens and reads Michael's letter. ("Secrets")
- Jonas, Martha, Bartosz, Magnus, Mikkel and Franziska go to the caves to take Erik's drug stash. They hear strange noises and the lights begin to flicker, so they run away. Mikkel goes missing. ("Secrets")
- Mads Nielsen's body appears from 1986 in the bunker, this being witnessed by Peter Doppler, who tells Tronte Nielsen. Eventually Claudia Tiedemann shows up and tells them to dispose of the body somewhere it can be found.
- An unknown corpse is found dead with charred eyes in the forest. ("Secrets")
- Ulrich finds a locked door in the caves, property of the nuclear plant.
- Older Jonas comes out of the caves with a suitcase and settles in Regina's hotel.
- Jonas finds a map of the caves in his father's room.
- Aleksander Tiedemann secretly orders the digging up of the radioactive waste barrels and the loading of them into a truck.
- Jonas starts exploring the caves.
- Charlotte Doppler suspects her husband has been cheating on her during the last year and suspects he's involved in the case.
- Ulrich illegally enters the nuclear plant to investigate.
- Elisabeth Doppler meets Noah on her way to her house, and he gives her a pocket watch for her mother Charlotte.
- Yasin Friese disappears in the woods, kidnapped by Noah's henchman.
- Noah contacts Bartosz through Erik's phone and meets him in a limousine. He tells him what will happen in the following days.
- Ulrich breaks the affair he's been having with Hannah Kahnwald.
- Jonas receives a package from his future self containing a lantern and a very aged version of his father's suicide note, where he reveals his past and his true identity, Mikkel Nielsen.
- Regina is diagnosed with breast cancer.
- Katharina finds out about Ulrich and Hannah's affair.
- Jonas finds the portal in the cave and travels to 1986.
- Ulrich finds out the dead boy found in the forest could be in fact his brother Mads.
- Charlotte executes a search warrant at the nuclear plant.
- Charlotte finds the area where the nuclear waste used to be buried, now empty, but with traces of paint.
- Ulrich visits Helge and tries to extract some information from him. He makes Helge very upset and is thrown out.
- Charlotte goes to the bunker and finds a piece of the old wallpaper used in 1986 during the kidnappings.
- Helge runs away from the nursing home to try and stop his past self. He travels to 1986.
- Ulrich comes back to see Helge and finds the book A journey through time. He follows Helge into the caves and travels to 1953.
- Jonas gets home and decides not to tell his mom about his father's true identity or the time-travelling and burns Michael's suicide letter.
- Claudia Tiedemann visits her grandson Bartosz and tells him to give his mother a certain photo.
- Hannah Kahnwald blackmails Aleksander Tiedemann into destroying Ulrich, since she has proof that Aleksander is an impostor.
- Bartosz meets again with Noah, who had presented him an offer the last time.
- Older Jonas extracts a sample of a substance from the radioactive waste barrels in the truck.
- Jonas travels to 1986 to bring back Mikkel.
- Charlotte finds a newspaper from 1953 with a picture of Ulrich locked in a cell.
- Bartosz joins Noah's side after being manipulated by him and learning about time travel.
- Due to Germany's government staggered plan to phase out nuclear energy sites, the Winden power plant is decommissioned and taken off the grid. This facility has the longest record of failure free operations in Germany.
- Tuesday 12th: Jonas arrives to 2052, only to find a war-torn Winden. While searching Jonas gets knocked out by survivors who are clearly waiting for him.