With today’s release of the first theatrical trailer for the The Dark Tower, we got some much-needed plot details for the film. But, in doing so, the trailer sort of spoils the aim of Roland’s quest throughout the entire book series. Here’s why:

Mild spoilers ahead for the entire Dark Tower series by Stephen King.

Before the full trailer dropped on Wednesday, little was known about the plot of The Dark Tower movie beyond Roland Deschain (Idris Elba) and his relentless pursuit of the Man in Black (Matthew McConaughey). Even after Tuesday’s cute Twitter banter, things were still murky.

But now, the trailer has delivered on some serious gunslinging action in both what we’d call “our world” and the world Roland hails from, called “Mid-World.” And just talking about Mid-World itself, is a spoiler.

In the first book in Stephen King’s eight-book series, The Dark Tower I: The Gunslinger Roland does indeed meet young Jake Chambers and adopt him as his companion, but the two spend all of their time hunting down the Man in Black in Mid-World as the titular Dark Tower lingers as some enigmatic objective in their distant future, one that Roland himself doesn’t fully comprehend. But Elba’s Roland has a pretty clear grasp on what he needs to do: prevent the destruction of the Tower itself, because that would basically destroy the multiverse.

In this film version, Roland tells Jake, “The Tower protects both our worlds. If it falls, hell will be unleashed,” which, well, pretty much spoils a lot of the lore that’s only exposed in later books in the series. Also in the trailer, Roland and Jake are seen venturing to Earth together, which to some extent rewrites the narrative of the books entirely.

But all of these discrepancies might be moot if the image Stephen King teased last May featuring the Horn of Eld turns out to be true. If Idris Elba’s Roland does indeed carry the Horn of Eld, then that means his entire journey will be a different one than the book readers know. But regardless, we now know exactly how the Tower functions and what Roland needs to do to prevent the demise of the multiverse, which is kind of a bummer.

Watch the action-packed trailer for The Dark Tower here:

The Dark Tower hits theaters August 4, 2017.