In Dark season the two worlds were known as the Knot and were linked in an infinite loop which meant certain events always had to play out the same way like Noah (Mark Waschke) being unable to shoot dead his nemesis.
They only found this out after Claudia Tiedemann (Julika Jenkins), who had slowly pieced together everything through various cycles.
She sent Jonas and Martha Nielsen (Lisa Vicari) to the Origin World and told them how they could break the Knot.
The teens succeeded and it meant the Knot could finally end with the apocalypse never happening in the first place.
Ultimately, all the characters were at peace as the Knot was destroyed and they could rest in nothingness.
However, given Claudia knew all about the Knot and the Origin World, it seemed odd she wasn’t the one to bring it all to an end.
This seems to be something of a plot hole. If Claudia figured out the origin of the Knot then surely she could have been the one to simply go through time and change events herself?
Perhaps Martha and Jonas had to be the ones to break because their child was also at the centre of the Knot.
The pair became Adam (Dietrich Hollinderbäumer) and Eva (Barbara Nüsse) after all, who are locked in an eternal battle with one trying to break the cycle and the other trying to preserve it.