But then, during a final D&D campaign in the very last scene, Mike (Finn Wolfhard) puts forward an alternative theory. What if the image they all saw of El standing in the doorway to the Upside-Down was really just a projection made by Eight/Kali (Linnea Berthelsen)? Could it be that the real El actually made a pact with her fellow Hawkins Lab survivor, managed to slip back into the real world while everyone was distracted, and is now living out her days in another part of the world under a new identity as Mike’s story suggests?

The Duffer Brothers’ show refuses to confirm what really happens — but some fans are speculating that the clues point to El being alive.

What’s the clue on the bookshelf?

One of these clues is on the bookshelf in the Wheeler’s basement at the very end of the episode, where the main gang go and return their D&D campaign binders once and for all. In the episode itself it’s hard to read the titles of the books surrounding the binders — but in one of the behind-the-scenes images posted on Instagram by Stranger Things star Noah Schnapp, we can get a clearer look (swipe through to the final image).

As fans have already pointed out on Reddit, one of the books is The Empty Copper Sea by John D. MacDonald — a 1978 novel about a detective investigating a possible faked death.

It seems highly unlikely this choice by the Stranger Things production team is a coincidence, so could it be another hint that Mike’s theory about El is correct? Maybe. Although if you were being cynical, you could also argue that a grieving Mike may just have spent the past 18 months reading stories about fake deaths while he was working on his own theory about El.