Stranger Things fans will remember being introduced to season one’s main villain Dr. Brenner (played by Matthew Modine), who was the reason Eleven (Millie Bobby Brown) spent most of her childhood in Hawkins lab.
After separating Eleven from her mother at birth, Brenner raised El in Hawkins lab, putting her through rigorous tests and unleashing terrifying monsters to push her to the limits of her psychic abilities.
The season one finale of the Netflix Sci-fi presumably saw him killed off after he began to lose control over the monster he created.
However, one fan theory predicts the Lab director is still alive, and could make a comeback should there be a season four.
Reddit user kony_stark took to the site to share his speculation that the American is actually Dr. Brenner.
The user said: “I believe that the American that the Russians mentioned in the mid credit scene is actually Dr. Brenner, AKA Papa from season 1.
“He was confirmed alive in season 2 and I believe the Russians have been using him for his science in their attempt to access the Upside Down.”
Fans may be wondering how Dr. Brenner would have survived the vicious attack from the Demogorgons.
However, the theory isn’t too far fetched as fans will remember the season two finale saw former agent for the department of energy Ray Carroll (Pruitt Taylor Vince) claim that Brenner is still alive.
Could Ray be referring to the Russian prison sited in the season three finale?
READ MORE: Stranger Things season 4: Is Eleven actually Hopper’s daughter?
If so, the next outing could see Dr. Brenner and Eleven reunite, after all she does need her powers back and who better to guide her than the man who helped create them?
The user is not the only fan who speculates Dr. Brenner is still alive as Reddit user JediSabre predicted the next outing could see the doctor return in the search for Eleven’s powers.
The user theorised the answers to finding Brenner could be in Chicago, where Eleven met fellow lab subject Kali (Linnea Berthelsen) in season two.
The next outing could see Mike Wheeler (Finn Wolfhard) goes on an epic mission to find her in a bid to find Dr. Brenner and get Eleven’s powers back.
Could Dr. Brenner return and help Eleven regain her powers?
The user theorised: “After Eleven and Mike fight about her powers, Mike decides to pull a Ferris Bueller, and with Dustin, Lucas and Max, heads to Chicago to track down Kali.
“She’s been on the hunt for Dr Brenner since she was told he was alive.
“Mike wants to help her find Brenner so he can confront him about the chemicals they used on Eleven.”
Could Mike track down Kali and Brenner and uncover what gave Eleven her powers?
Stranger Things series 3 is now available to stream on Netflix.