Stranger Things drops season 4 teaser trailer featuring surprise returning character

Posted on the official Stranger Things Twitter account alongside the caption, "Eleven, are you listening?" the teaser is set inside the Hawkins National Laboratory, beginning with footage of several children playing as ominous music is heard in the background.

We are then reintroduced to Dr. Martin Brenner (Matthew Modine) – the scientist in charge of the lab, who was a major villain in the first season – as he enters the lab, saying, "Good morning, children."

He later continues, "Today I have something very special planned for you."

The camera then focuses on the door of Eleven's old room, before Brenner rather chillingly says, "Eleven are you listening?"

In the final shot of the teaser, we see Eleven's eyes suddenly jolt open and it appears Brenner's message has reached her.

The significance of all this remains unclear and it is likely fans will find themselves with more questions than ever, especially relating to the appearance of Brenner, who appeared to have been killed off by the Demogorgon in the first run.

Interestingly, Modine did give an interview last year revealing that his character could still be alive, with the actor telling NME, "The show's creators, the Duffer Brothers, have said that unless you see a body, the character's not dead. And obviously we never saw Dr. Brenner's body."

Plot details about the fourth run have largely been kept under wraps, but a few details have emerged, including the fact that a major storyline will involve Hopper, who survived the events of season three and is now being held hostage in Russia.

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We also know of a few new actors joining the series for season four, including Booksmart star Eduardo Franco, The Twilight Saga's Jamie Campbell Bower, and Freddie Krueger himself Robert Englund.

Filming has been severely impacted by the coronavirus pandemic and so it's possible we won't see the new series until early 2022 but, according to star Noah Schnapp, filming is set to finish this summer.

Stranger Things season four has been delayed, but seasons 1-3 are now available on Netflix. Check out our guides to the best series on Netflix and the best movies on Netflix. If you’re looking for more to watch, check out our TV Guide.