So... first two seasons were absolutely brilliant. There's couple of tiny inconsistencies but I'm willing to forgive those. It was done brilliantly and the tone was just right. Also, I think this is one of those rare Time Travel shows where they got the idea right (well, consistent is a better word I guess since we don't know what's right and wrong, if at all possible, when it comes to time travel) and was thoroughly enjoyable. The only thing that didn't make sense was that by end of S1, Beard Jonas trying to destroy the cave thing. As we learn in S2, the younger Jonas learns that destroying it won't be helpful, but years later his older self does it anyway. With conviction that it's going to fix everything. But ok.

However, S3 was a disappointment imo. The brilliance of S1 and S2 was that they stuck to the One-World Theory and made it work. As soon as you bring in multiple universes it's just too easy. At that point anything goes; you can make up shit as you go along and say this is because of that. Like that infinity symbol outer/inner edge thing they used to explain two worlds; in first seasons they just laid out few basic rules like 'what happened will always happen' thus circumventing Grandfather Paradox, and made it work. But now you can pull shit from thin air, like the 3rd world. For me it just took the magic away of first two seasons.

So I would give 5/5 for first two seasons but 3.5 or 4/5 for the last, overall maybe 4.

The good stuff.

How about casting!?!?! Like seriously, I could identify the younger/older selves of our characters RIGHT AWAY most of the time. That has to be some feat getting actors to work that well. Like, I thought older Ulrich was the middle age guy with makeup, only to realize its two different actors. Young and middle aged Jonas are great, so is old and young Marthas. Peter and younger self are like carbon copies, Catharina old and young selves. Bartosch. Damn the list goes on.

Jonas and Martha had some amazing (if annoying) chemistry. Jonas was deadpan to the point I wanted to hit the guy in the head, but I think they worked great as a couple. And most other actors did justice too.

Attention to smaller details too. They used this thing were everything was flipped horizontally between two worlds (Martha's cut keep jumping from left to right), all houses have orientation flipped, things like that. Even I remember a case in S2 where young Mikkel was in police office when he went back to 80s, and solves the rubic's cube. In subsequent scenes you can see the solved cube. Tiny things like that were pretty cool.

Overall one of the best shows in recent times, SciFi or otherwise.

Re. the quantum entanglement. This is kinda what I meant, quantum entanglement has nothing to do with this concept; QE means two particles that are physically separated can still 'communicate' with each other even when billions of miles away, and do that instantaneously, so they maintain same momentum, spin, etc. Here they just threw that word so that they could say two split timelines move alongside each other, but that's not quite what QE means. The two timelines don't really 'entangled' in the sense that they do the same thing; in fact they just go their own ways although people can move between. They just introduced a concept and threw a fancy word at it.

My larger point being, a story is hardest to execute but well rewarded if premises are fewest. This is why a story like Matrix is so brilliant; the central premise that machines would harvest humans for power is utter bollocks - we make such poor batteries. But once you buy into the premise, everything else just works from there flawlessly. Likewise in first two seasons there was only two premises that we needed to buy into without questioning: 1) that the Higg's Boson can somehow facilitate time travel and that 2) when traveling in time Grandfather Paradox isn't a problem because you can't change the past because it's already happened. That's the only thing that we needed to buy into and they executed the rest perfectly. It's hard to pull off but rewarding.

But in S3 they brought forward a ton of new concepts; timelines can split, both worlds(universe) we followed were spun off of an original world, that you can travel between worlds/universes not just time. All this means we have to agree to all their premises and that makes the storytelling easy; they can pull out an excuse every time they want a plot to move forward. So I no longer was awed during S3 like I was in S1 and 2, because it's like they're saying hey, this is because this new concept, go along with it.

I'm not saying it's bad, it still very well executed great show, but that S3 kinda diluted the whole thing. Obviously this is just my opinion.

At the end of the day, it's a great show and very much enjoyable. And refreshing to see a non Hollywood story too.