Spoiler Jonas is both alive and dead. Here: https://www.inverse.com/entertainment/dark-season-3-theory-finale-schrodingers-cat This is the best explanation I've seen. It's also why the show goes through such trouble to inform its audience on Schrödinger's cat. In quantum physics, subatomic particles exist in completely different states at the same time. Spoiler That's what I was remembering. But oh well, I only watched the season once, and you admitted how many details you forgot. It doesn't change what I'm saying though. The relationship between the separate worlds isn't temporal. You're complaining that the show violated its own rules by the end when what it did introduce entirely new rules. Similarly, quantum physics doesn't obviate general relativity; it just introduces new rules. No need for spoilers here. It's like you want a logical, linear explanation for a show whose entire foundation is a fucking paradox. I don't know what to tell you, bub.