Think about all the events that happened in this tv series in the context of quantum and Einstein's theory of relativity. In short, quantum is about all the possibilities that can happen in the reality. For example, parallel universes have different what-if scenarios of real life. For example, in the universe A you are a male human but in the universe B you are a female cat. Et cetera. And Einstein's theory of relativity is about... well relativity of reality so for example you look at the sky during a clear night and see a star shining brightly but the star has perhaps long gone but its light just reached to you so you think star still exist when it's not anymore. In that context what you think happened now sometimes actually happened in future and sometimes what happened in the future happened in the past et cetera.

In this tv series, for some reason, the universe is buggy therefore what normally shouldn't happen happens perhaps because the end of the universe is coming and this is how armageddon is or perhaps because of a different reason which I'll mention at the end of my theory or perhaps this is how it's supposed to be if certain condition happens in real life.

According to Einstein's theory of relativity, the future has already happened so we are like in a train reaching a particular destination but also there are a lot of trains in this reality so all these trains reach to their own different destinations. All trains are on their own different tracks. But imagine what would be like if there is a train inside of a train which normally doesn't happen? It would be like what happened in this tv series.

But the thing is, imagine a train left its track and started to move on a different track by getting inside of another train and therefore missed its destination it should have reached. I think that's the reason for the time loop happening in this tv series. So it's like the universe trying to make a particular future happen so the reality can continue to exist as how it should exist but because a particular future that had to happen didn't happen, another universe is created which I'll call it a pocket universe (universe inside of a universe (train inside of a train)) and this pocket universe will continue to exist as a reaction of the universe for making a particular future happen in the universe.

Perhaps we gotta stop thinking the future happens because of the past, therefore instead, for now, we should think the past happens because of the future hence why the time loop happens until a particular future happens because without that future the past events can't happen.

So let's start from the basics:

How many universes there are in this tv series?

There are 5 main universes:

-In universe A, Nadia and Alan are still alive which in this universe past events happen before the time loop. So, kid Nadia and her mother are alive in this universe.

-In universe B Nadia and Alan are dead because this universe came into existence after Nadia and Alan died in universe A.

-In universe C time loop happens. The universe C was created when the time loop started.

-In universe A1 there are Nadia from universe C and Alan who is from universe A.

-In universe A2 there are Alan from universe C and Nadia from universe A.

So I think in the exact moment when the time loop started, for some reason universe C is created inside of universe A therefore past events are happening in the universe C but future events didn't happen but I'll assume universe B exist.

What are the facts that are valid in real life which can be used to explain this TV series?

Energy never just disappears, they just transform into another type of energy.

Opposite energies attract each other.

Everything exists because of its opposite.

What did I notice?

I noticed certain objects are connected with other objects and I'll even consider kid Nadia, current Nadia and Alan as objects. For example, Alan's fish is connected to Alan and Nadia's book, mirrors, kid Nadia, etc. Are all connected to Nadia.

Why do certain objects disappear and appear?

I think every time Nadia and Alan dies, a new universe C is created because a certain future has to happen so universe A can continue to exist in however the way it should. But I think universe C is created by the objects that are related to Nadia and Alan. And it seems like the next universe C is created according to what happened in previous universe C therefore what happens with the objects changes every time a new universe C is created. Like for example, Nadia's cat disappears but sometimes it doesn't.

So don't think it as time rewinds when they die. They die but as a result, a new Nadia and Alan are also created. It's just that, their mind is also copied and pasted into the new Nadia and Alan therefore they can remember what happened before they die. Why their mind is copied and pasted to their new self is because a new universe C using the objects to create itself by using the previous objects from universe C that also universe A have. Objects are all connected to each other in energy level because they all share the energy field generated by Nadia and Alan which this energy field generated by their emotions.

The thing is, also a new type of universe B is created every time they died like universe B1, universe B2, et cetera.

Then why objects disappear and appear? I think there is a dream-like logic here. For example, you can't drive a car and your dream will end when you try to drive a car if you never drove a car before because your brain doesn't have the necessary "objects" to continue the dream. So I think characters die every time they do something they wouldn't because the universe C doesn't have the necessary objects to continue the reality.

How they die is really dream-like as in normally such stuff shouldn't happen like how it happens in real life. The reasons that kill them are always by the objects that exist in universe A and therefore they exist in universe C too. The thing is, when there was no more "make sense" way to kill Nadia, her kid self started to appear so Nadia can have a heart attack and therefore die. And when Nadia resisted having a heart attack by seeing her past self, a sharp glass piece appeared inside of her so she can die.

What else I did notice?

The objects have emotional meanings for Nadia and Alan therefore they have the power to affect the universe C. Like for example mirror, fish, kid Nadia, et cetera.

There is an undeniable relation to emotions and objects in the TV series. For example, Alan's fish disappeared after he forgot to feed it and it came back when Alan realized his fish is gone. It's like Nadia's and Alan's emotions changes how new universe C will be because the new universe C is created by the objects from the previous universe C.

In that context, I think that's why mirrors disappeared and kid Nadia started to appear because Nadia started to talk about her past. Nadia probably wanted to forget about mirrors because of her past therefore they disappeared.

How/why Nadia and Alan are connected?

When the time loop started Nadia was sad and Alan was happy at the same time and when Alan and Nadia died, Nadia was happy to see her cat and Alan was sad at the same time. That's some connection they have in common other than they are both human and they live somewhere close.

But their opposite aspects are more important than what's common about them because opposite stuff attracts each other.

For example, Nadia is a free spirit so she does whatever she wants but Alan always limits himself. So personality-wise they are very opposites. It's like, if Nadia and Alan had to be electricity: Nadia would be + and Alan would be -. But you know there is a 3rd charge in electricity which is 0 charge, then who could be this person?

There is one more thing common about Nadia and Alan: They both died indirectly because of one person in universe A. This person's name is Mike Kershaw and he is the 0 charge person. His personality neither positive nor negative and how he affected Nadia's and Alan's life is how 0 charge affects + and - charges.

Reminder for what Mike did to make Nadia and Alan die indirectly: Mike went to Nadia's house with her which by doing so he just changed Nadia's destiny. Mike has an affair with Alan's GF so because of it Alan suicided.

Pay attention to the fact that Nadia and Alan got out of the universe C when Alan made his peace with his GF so he won't suicide because of Mike. Also, I think they would return to universe C if Nadia died because of Mike and because Alan couldn't save Nadia.

Why Nadia and Alan die at the same time?

The only logical idea I have is, Nadia and Alan are so opposite but somehow they are the same kind of energy type, they attracted each other in a way they became one. Perhaps universe C couldn't happen if they didn't become one because everything exists because of its opposite.

Why Nadia and Alan start the loop in a particular moment?

It's because it was the last time they were both happy at the same time before they died.

Why Nadia and Alan from universe C ain't in the same universe anymore?

Because in the last universe C, Alan made peace with his GF but Nadia and Alan died before Nadia fixed her issues about her mother.

You mentioned "perhaps because of a different reason which I'll mention at the end of my theory". What's that?

Well, in many religions parallel universes are believed in by many people even though some of them ain't aware what they believe in is a parallel universe. They call these universes "hell" and "heaven" et cetera. They also believe your spirit as energy transforms into something else or your life energy transforms into sprit, et cetera. So perhaps when you die, your energy transforms and creates a pocket universe and therefore you are stuck in a time loop.