24 questions the 'Stranger Things 4' finale left unanswered

Earlier in the series, we were told that Eleven's powers were the result of an experiment done with her mother that included drugs like LSD and time spent in sensory deprivation tanks when she was pregnant.

But in the flashbacks to young Henry's life, he simply says that he became aware of his abilities when he was a young boy.

So where did they come from? Something else supernatural? A chemical experiment his father was a part of during World War II?

This season, "Stranger Things" revealed that Hopper was making Agent Orange (a deadly chemical weapon used in the Vietnam War) as a teenager. In his monologue to Alexei, Hopper says he believed his daughter's illness was the result of Agent Orange, given that he handled it so often without any protection.

There seems to be a link between Eleven's mom getting experimented on by the government, Hopper's daughter dying as a result of government-led chemical warfare, and Victor Creel's son manifesting mysterious powers.

We could be wrong, but it'd be awesome to get more answers about why Hopper's backstory became more relevant this season again.

As we noted in our breakdown of the details you might have missed in "Stranger Things" season four, the flashback to Eleven's attempted escape from Hawkins Lab shows her running down a familiar flight of stairs.

Hopper was in that same stairwell when he was grieving over his daughter's death in a hospital room. Does that mean Sara died inside HNL? This season we got the reveal that Hopper believes that Sara died due to birth defects related to Agent Orange. But why would that have landed her in the secret hospital lab in Hawkins?

Insider asked Harbour back in 2017 if he could tell us more about this connection between Sara's hospital room and the HNL.

"Hmmmm [laughing] I can not," Harbour said. "But yes, it is the same location. So that's interesting. Or it's a similar location. But there's actually another thing you'll notice which is that there's a stuffed animal lion that appears in Eleven's room when he breaks into the lab and finds that room, and it also appears in Castle Byers, and it also appears on Sara's lap."

For a full breakdown of all the connections between Hopper, his daughter Sara, and Eleven, read our full report here.

We know all about Eleven's mother, Terry Ives. But so far "Stranger Things" has yet to tell fans anything about Eleven's father.

Is it literally Dr. Brenner? If so, that makes his experiments and behavior even more disturbing, given the torture and emotional abuse the children suffered inside Hawkins National Lab.

And if it's not Brenner, then will we learn who the real father was sometime before the series comes to an end?

Maybe it's really Henry (who is about 25 years older than Eleven), in which case "Stranger Things" is setting up a Luke Skywalker/Darth Vader-style showdown for the fifth and final season.

One of the strangest details about the gruesome way Henry (aka Vecna or One) murders people is by sucking their eyes into their heads, leaving blank and bloody sockets behind.

What's up with that? Does killing people in this ritualistic way somehow make him stronger? Or give him more insight into Hawkins?

We know Will happened to live close to the Hawkins Lab and was also struggling emotionally in his life before he was pulled into the Upside Down. Not only was Will bullied at school by the kids we saw picking on Dustin, Lucas, and Mike, but in the pilot episode, Joyce says that Will's dad was emotionally abusive towards him as well.

Maybe it's simply that this extra sensitivity made Will an ideal victim for Henry. But is there a larger reason behind Will's connection to the Upside Down that made him the target for Henry's plot?

When Mike brought Eleven to his house, she saw a photo of Will and recognized him. Mike hadn't even mentioned that Will was missing, but Eleven somehow knew not only who Will was but where he was.

How? When would she have seen him before?

There's still a lot unknown about the time between Eleven re-opening the Gate to the Upside Down and her escape into Hawkins — and we want some answers!

In "Stranger Things" season four, Nancy realizes that the Upside Down is an exact mimic of the real Hawkins — but says it's frozen on the day Will went missing in 1983 (November 6). That means any changes made in Hawkins since that date aren't reflected in the alternate dimension.

But that's not how the Upside Down worked in the past. Joyce was able to put up the lights and letters in Hawkins and have them reflected in the Upside Down immediately, allowing Will to see the letters and communicate with her by selecting lights over letters to spell out "R-U-N."

So as far as we can tell, the Upside Down used to mirror real-world changes in real-time. But now it's not? How come?

Did it perhaps revert back to that date for some reason? Is there a bigger connection between Henry and Will's disappearance than we realize?

While manipulating Eleven into helping him, Henry advises her to use a memory from her past that made her both sad and angry. He says that "One" (himself) learned how to become more powerful by tapping into a memory like that.

But what was his earliest sad memory? In his flashbacks, we don't see anything particularly bad happening to young Henry Creel. Perhaps there's more to his backstory (and the revelation of how he got his powers) than meets the eye.

In "Stranger Things" season two, Eleven met her "lost sister" — Kali Prasad. She's tattooed with "008" on her wrist and has illusion powers that seem similar to what Henry can do.

Some people may be inclined to think that Kali is simply gone from the story forever, but then why would the "Stranger Things" crew go through the trouble of putting a reference to her in the very first episode of season four? As we outlined in our breakdown of the best details you might have missed in "Stranger Things" this season, Brenner's crossword puzzle included the name Kali as an answer.

So will she come back into the story for season five? Her powers combined with Eleven's could be very useful in defeating Henry once and for all.

In earlier seasons, it seemed like the Upside Down was simply a mirror dimension to Earth and everything inside was the same as the real world — just creepier and populated with scary creatures instead of humans.

But this season we learned that Henry was first sent to this strange dimension by Eleven. And when Henry arrived, the landscape was desolate with a yellow tinge — not the red/blue hues we're used to seeing in the Upside Down.

So how did it transform? Did Henry himself create a fake model of the town of Hawkins, if that's where he last lived? One fan theory posits that Will might have been the one to Hawkins-ify the Upside Down. If so, does that mean Will can undo parts of the Upside Down?

This is likely an inconsequential detail about the creepy physical form Henry has taken on, but we were left wondering if there's a reason why his left hand is so much larger and scarier than his right hand.

Nancy does seem to be the de facto leader of all the teens and young adults in "Stranger Things," so maybe Henry decided to use her as the vehicle for his threat.

But we wonder if there may be another important reason why Nancy survived without so much as a scratch after so many other people were killed or injured this season.

Nancy says she saw a "giant creature with a gaping mouth" when Vecna took over her mind.

She's seen the Demogorgon, demodogs, demobats, and Mind Flayer, so if it was one of those creatures, she would have just named it.

What new horrors are in store for Hawkins? What other monsters?

And what about her vision of her mom, Holly, and Mike all dead? That didn't happen in the "earthquake" during the final moments of the season, so is that fated to happen in season five?

Last we saw Dr. Owens, he was handcuffed to a pole in the abandoned military base. Was he left alive? Did his associates rescue him? One of the agents helping Owens told Hopper that the doctor was just indisposed, so we're hoping that means he isn't dead yet.

Eleven narrowly escaped the assassination attempt carried out by Sullivan and his soldiers, but we doubt she'll be left alone for much longer.

Will the military threat resurface in season five? Or will they have realized that she wasn't responsible for the disasters plaguing Hawkins?

The Russian scientists operating out of a prison not only had a live Demogorgon they were operating on, but had also managed to contain the cloud-like particles that Henry used to create the Mind Flayer.

How did they do that? And what have they learned about how the particles work?

In the opening scene of episode nine, you can hear Murray in the background telling Dimitri that he would fit in Indiana.

Did he move there, since he's now a wanted traitor in the Soviet Union? And what about Yuri?

Henry hadn't managed to complete the ritualistic killing of Max (her eyes were still intact, and one of her arms was left unbroken), but she seemed to succumb to her injuries after a few minutes.

Eleven saw Max die while she was in the Void — that black liminal space where Eleven is able to use her powers to see people far away. But Eleven refused to give up and seemed to be preparing to use her powers to save Max.

The screen cut to black, and we later learn that Max's heartbeat stopped for a long time before starting again. This appears to be Eleven's doing, but the show hasn't yet explained to us how or why this happened.

In the massacre flashbacks, Henry tells Eleven that the dead children are still with him, but he doesn't explain what that means.

We also saw the bodies of his Hawkins victims inside his mind lair. Is he somehow holding people's consciousness hostage after destroying their physical bodies? If so, does that mean Max's consciousness could possibly be reunited with her body?

In the first part of "Stranger Things" season four, Max realized she was being stalked by Henry and decided to write letters to her mom and closest friends in case she died. As far as we know, all those people still have the sealed letters from Max that she said to read after she was gone.

Though she hasn't technically died yet, will any of those people decide to read the letters? Could there be clues inside that will help Eleven rescue her consciousness?

This season was the closest the parents came to actually understanding all the dangerous adventures their children have been up to for the last year. But even after a dramatic town hall scene and extensive conversations with the Hawkins police, the parents of all the kids seemed to disappear from the plot.

Will we finally see the parents get involved next season? Or are they truly just meant as a stand-in for the real neglectful parenting methodologies of the 1980s?

Eddie's death was one of the most heartbreaking moments of season four, primarily due to the incredible acting performances given by Joseph Quinn (Eddie) and Gaten Matarazzo (Dustin).

But we didn't see any of the other kids or teens react to his death, since they were all elsewhere in the Upside Down or in the real world when it happened. How did Steve and Nancy and Robin feel about it? Or Mike and Lucas?

Not to mention, what the heck did they do with the body? Is Eddie's body still in the Upside Down?

To end on a lighter note, we hope there's a payoff in season five for the moment when Erica threatened her older brother with an embarrassing reveal. So what is Lucas keeping under his bed? Something scandalous, or really nerdy?

Hopefully, we'll find out the answer to some of these questions in the next couple of years. In the meantime, read everything the Duffer Brothers have said so far about the fifth and final season here.